diff --git a/core/modules/file/file.module b/core/modules/file/file.module
index 9f37d13..8262e39 100644
--- a/core/modules/file/file.module
+++ b/core/modules/file/file.module
@@ -726,13 +726,12 @@ function file_save_upload_from_form($element, FormStateInterface $form_state, $d
           '#items' => $new_errors,
         ),
       );
-      $error_message = \Drupal::service('renderer')->renderer->renderPlain($render_array);
+      $error_message = \Drupal::service('renderer')->renderPlain($render_array);
     }
     else {
       $error_message = reset($new_errors);
     }
 
-    \Drupal::logger('file')->notice('The file upload failed. %upload', array('%upload' => $upload_name));
     $form_state->setError($element, $error_message);
 
     // Empty the old queue and put the errors back as before.
@@ -1268,6 +1267,7 @@ function file_managed_file_save_upload($element, FormStateInterface $form_state)
   $files_uploaded |= !$element['#multiple'] && !empty($file_upload);
   if ($files_uploaded) {
     if (!$files = file_save_upload_from_form($element, $form_state)) {
+      \Drupal::logger('file')->notice('The file upload failed. %upload', array('%upload' => $upload_name));
       return array();
     }
 
diff --git a/core/modules/file/src/Tests/SaveUploadFormTest.php b/core/modules/file/src/Tests/SaveUploadFormTest.php
new file mode 100644
index 0000000..5d7f89f
--- /dev/null
+++ b/core/modules/file/src/Tests/SaveUploadFormTest.php
@@ -0,0 +1,365 @@
+<?php
+
+namespace Drupal\file\Tests;
+
+use Drupal\file\Entity\File;
+
+/**
+ * Tests the file_save_upload_from_form() function.
+ *
+ * @group file
+ *
+ * @see file_save_upload_from_form()
+ */
+class SaveUploadFormTest extends FileManagedTestBase {
+
+  /**
+   * Modules to enable.
+   *
+   * @var array
+   */
+  public static $modules = ['dblog'];
+
+  /**
+   * An image file path for uploading.
+   *
+   * @var \Drupal\file\FileInterface
+   */
+  protected $image;
+
+  /**
+   * A PHP file path for upload security testing.
+   */
+  protected $phpfile;
+
+  /**
+   * The largest file id when the test starts.
+   */
+  protected $maxFidBefore;
+
+  /**
+   * Extension of the image filename.
+   *
+   * @var string
+   */
+  protected $imageExtension;
+
+  protected function setUp() {
+    parent::setUp();
+    $account = $this->drupalCreateUser(array('access site reports'));
+    $this->drupalLogin($account);
+
+    $image_files = $this->drupalGetTestFiles('image');
+    $this->image = File::create((array) current($image_files));
+
+    list(, $this->imageExtension) = explode('.', $this->image->getFilename());
+    $this->assertTrue(is_file($this->image->getFileUri()), "The image file we're going to upload exists.");
+
+    $this->phpfile = current($this->drupalGetTestFiles('php'));
+    $this->assertTrue(is_file($this->phpfile->uri), 'The PHP file we are going to upload exists.');
+
+    $this->maxFidBefore = db_query('SELECT MAX(fid) AS fid FROM {file_managed}')->fetchField();
+
+    // Upload with replace to guarantee there's something there.
+    $edit = array(
+      'file_test_replace' => FILE_EXISTS_REPLACE,
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri()),
+    );
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertRaw(t('You WIN!'), 'Found the success message.');
+
+    // Check that the correct hooks were called then clean out the hook
+    // counters.
+    $this->assertFileHooksCalled(array('validate', 'insert'));
+    file_test_reset();
+  }
+
+  /**
+   * Test the file_save_upload() function.
+   */
+  public function testNormal() {
+    $max_fid_after = db_query('SELECT MAX(fid) AS fid FROM {file_managed}')->fetchField();
+    $this->assertTrue($max_fid_after > $this->maxFidBefore, 'A new file was created.');
+    $file1 = File::load($max_fid_after);
+    $this->assertTrue($file1, 'Loaded the file.');
+    // MIME type of the uploaded image may be either image/jpeg or image/png.
+    $this->assertEqual(substr($file1->getMimeType(), 0, 5), 'image', 'A MIME type was set.');
+
+    // Reset the hook counters to get rid of the 'load' we just called.
+    file_test_reset();
+
+    // Upload a second file.
+    $image2 = current($this->drupalGetTestFiles('image'));
+    $edit = array('files[file_test_upload]' => drupal_realpath($image2->uri));
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertRaw(t('You WIN!'));
+    $max_fid_after = db_query('SELECT MAX(fid) AS fid FROM {file_managed}')->fetchField();
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate', 'insert'));
+
+    $file2 = File::load($max_fid_after);
+    $this->assertTrue($file2, 'Loaded the file');
+    // MIME type of the uploaded image may be either image/jpeg or image/png.
+    $this->assertEqual(substr($file2->getMimeType(), 0, 5), 'image', 'A MIME type was set.');
+
+    // Load both files using File::loadMultiple().
+    $files = File::loadMultiple(array($file1->id(), $file2->id()));
+    $this->assertTrue(isset($files[$file1->id()]), 'File was loaded successfully');
+    $this->assertTrue(isset($files[$file2->id()]), 'File was loaded successfully');
+
+    // Upload a third file to a subdirectory.
+    $image3 = current($this->drupalGetTestFiles('image'));
+    $image3_realpath = drupal_realpath($image3->uri);
+    $dir = $this->randomMachineName();
+    $edit = array(
+      'files[file_test_upload]' => $image3_realpath,
+      'file_subdir' => $dir,
+    );
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertRaw(t('You WIN!'));
+    $this->assertTrue(is_file('temporary://' . $dir . '/' . trim(drupal_basename($image3_realpath))));
+  }
+
+  /**
+   * Test extension handling.
+   */
+  public function testHandleExtension() {
+    // The file being tested is a .gif which is in the default safe list
+    // of extensions to allow when the extension validator isn't used. This is
+    // implicitly tested at the testNormal() test. Here we tell
+    // file_save_upload() to only allow ".foo".
+    $extensions = 'foo';
+    $edit = array(
+      'file_test_replace' => FILE_EXISTS_REPLACE,
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri()),
+      'extensions' => $extensions,
+    );
+
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $message = t('Only files with the following extensions are allowed:') . ' <em class="placeholder">' . $extensions . '</em>';
+    $this->assertRaw($message, 'Cannot upload a disallowed extension');
+    $this->assertRaw(t('Epic upload FAIL!'), 'Found the failure message.');
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate'));
+
+    // Reset the hook counters.
+    file_test_reset();
+
+    $extensions = 'foo ' . $this->imageExtension;
+    // Now tell file_save_upload() to allow the extension of our test image.
+    $edit = array(
+      'file_test_replace' => FILE_EXISTS_REPLACE,
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri()),
+      'extensions' => $extensions,
+    );
+
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertNoRaw(t('Only files with the following extensions are allowed:'), 'Can upload an allowed extension.');
+    $this->assertRaw(t('You WIN!'), 'Found the success message.');
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate', 'load', 'update'));
+
+    // Reset the hook counters.
+    file_test_reset();
+
+    // Now tell file_save_upload() to allow any extension.
+    $edit = array(
+      'file_test_replace' => FILE_EXISTS_REPLACE,
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri()),
+      'allow_all_extensions' => TRUE,
+    );
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertNoRaw(t('Only files with the following extensions are allowed:'), 'Can upload any extension.');
+    $this->assertRaw(t('You WIN!'), 'Found the success message.');
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate', 'load', 'update'));
+  }
+
+  /**
+   * Test dangerous file handling.
+   */
+  public function testHandleDangerousFile() {
+    $config = $this->config('system.file');
+    // Allow the .php extension and make sure it gets renamed to .txt for
+    // safety. Also check to make sure its MIME type was changed.
+    $edit = array(
+      'file_test_replace' => FILE_EXISTS_REPLACE,
+      'files[file_test_upload]' => drupal_realpath($this->phpfile->uri),
+      'is_image_file' => FALSE,
+      'extensions' => 'php',
+    );
+
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $message = t('For security reasons, your upload has been renamed to') . ' <em class="placeholder">' . $this->phpfile->filename . '.txt' . '</em>';
+    $this->assertRaw($message, 'Dangerous file was renamed.');
+    $this->assertRaw(t('File MIME type is text/plain.'), "Dangerous file's MIME type was changed.");
+    $this->assertRaw(t('You WIN!'), 'Found the success message.');
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate', 'insert'));
+
+    // Ensure dangerous files are not renamed when insecure uploads is TRUE.
+    // Turn on insecure uploads.
+    $config->set('allow_insecure_uploads', 1)->save();
+    // Reset the hook counters.
+    file_test_reset();
+
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertNoRaw(t('For security reasons, your upload has been renamed'), 'Found no security message.');
+    $this->assertRaw(t('File name is @filename', array('@filename' => $this->phpfile->filename)), 'Dangerous file was not renamed when insecure uploads is TRUE.');
+    $this->assertRaw(t('You WIN!'), 'Found the success message.');
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate', 'insert'));
+
+    // Turn off insecure uploads.
+    $config->set('allow_insecure_uploads', 0)->save();
+  }
+
+  /**
+   * Test file munge handling.
+   */
+  public function testHandleFileMunge() {
+    // Ensure insecure uploads are disabled for this test.
+    $this->config('system.file')->set('allow_insecure_uploads', 0)->save();
+    $this->image = file_move($this->image, $this->image->getFileUri() . '.foo.' . $this->imageExtension);
+
+    // Reset the hook counters to get rid of the 'move' we just called.
+    file_test_reset();
+
+    $extensions = $this->imageExtension;
+    $edit = array(
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri()),
+      'extensions' => $extensions,
+    );
+
+    $munged_filename = $this->image->getFilename();
+    $munged_filename = substr($munged_filename, 0, strrpos($munged_filename, '.'));
+    $munged_filename .= '_.' . $this->imageExtension;
+
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertRaw(t('For security reasons, your upload has been renamed'), 'Found security message.');
+    $this->assertRaw(t('File name is @filename', array('@filename' => $munged_filename)), 'File was successfully munged.');
+    $this->assertRaw(t('You WIN!'), 'Found the success message.');
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate', 'insert'));
+
+    // Ensure we don't munge files if we're allowing any extension.
+    // Reset the hook counters.
+    file_test_reset();
+
+    $edit = array(
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri()),
+      'allow_all_extensions' => TRUE,
+    );
+
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertNoRaw(t('For security reasons, your upload has been renamed'), 'Found no security message.');
+    $this->assertRaw(t('File name is @filename', array('@filename' => $this->image->getFilename())), 'File was not munged when allowing any extension.');
+    $this->assertRaw(t('You WIN!'), 'Found the success message.');
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate', 'insert'));
+  }
+
+  /**
+   * Test renaming when uploading over a file that already exists.
+   */
+  public function testExistingRename() {
+    $edit = array(
+      'file_test_replace' => FILE_EXISTS_RENAME,
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri())
+    );
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertRaw(t('You WIN!'), 'Found the success message.');
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate', 'insert'));
+  }
+
+  /**
+   * Test replacement when uploading over a file that already exists.
+   */
+  public function testExistingReplace() {
+    $edit = array(
+      'file_test_replace' => FILE_EXISTS_REPLACE,
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri())
+    );
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertRaw(t('You WIN!'), 'Found the success message.');
+
+    // Check that the correct hooks were called.
+    $this->assertFileHooksCalled(array('validate', 'load', 'update'));
+  }
+
+  /**
+   * Test for failure when uploading over a file that already exists.
+   */
+  public function testExistingError() {
+    $edit = array(
+      'file_test_replace' => FILE_EXISTS_ERROR,
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri())
+    );
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertRaw(t('Epic upload FAIL!'), 'Found the failure message.');
+
+    // Check that the no hooks were called while failing.
+    $this->assertFileHooksCalled(array());
+  }
+
+  /**
+   * Test for no failures when not uploading a file.
+   */
+  public function testNoUpload() {
+    $this->drupalPostForm('file-test/save_upload_from_form_test', array(), t('Submit'));
+    $this->assertNoRaw(t('Epic upload FAIL!'), 'Failure message not found.');
+  }
+
+  /**
+   * Tests for log entry on failing destination.
+   */
+  public function testDrupalMovingUploadedFileError() {
+    // Create a directory and make it not writable.
+    $test_directory = 'test_drupal_move_uploaded_file_fail';
+    drupal_mkdir('temporary://' . $test_directory, 0000);
+    $this->assertTrue(is_dir('temporary://' . $test_directory));
+
+    $edit = array(
+      'file_subdir' => $test_directory,
+      'files[file_test_upload]' => drupal_realpath($this->image->getFileUri())
+    );
+
+    \Drupal::state()->set('file_test.disable_error_collection', TRUE);
+    $this->drupalPostForm('file-test/save_upload_from_form_test', $edit, t('Submit'));
+    $this->assertResponse(200, 'Received a 200 response for posted test file.');
+    $this->assertRaw(t('File upload error. Could not move uploaded file.'), 'Found the failure message.');
+    $this->assertRaw(t('Epic upload FAIL!'), 'Found the failure message.');
+
+    // Uploading failed. Now check the log.
+    $this->drupalGet('admin/reports/dblog');
+    $this->assertResponse(200);
+    $this->assertRaw(t('Upload error. Could not move uploaded file @file to destination @destination.', array(
+      '@file' => $this->image->getFilename(),
+      '@destination' => 'temporary://' . $test_directory . '/' . $this->image->getFilename()
+    )), 'Found upload error log entry.');
+  }
+
+}
diff --git a/core/modules/file/tests/file_test/file_test.routing.yml b/core/modules/file/tests/file_test/file_test.routing.yml
index cdbf08e..1c5a763 100644
--- a/core/modules/file/tests/file_test/file_test.routing.yml
+++ b/core/modules/file/tests/file_test/file_test.routing.yml
@@ -4,3 +4,9 @@ file.test:
     _form: 'Drupal\file_test\Form\FileTestForm'
   requirements:
     _access: 'TRUE'
+file.save_upload_from_form_test:
+  path: '/file-test/save_upload_from_form_test'
+  defaults:
+    _form: 'Drupal\file_test\Form\FileTestSaveUploadFromForm'
+  requirements:
+    _access: 'TRUE'
diff --git a/core/modules/file/tests/file_test/src/Form/FileTestSaveUploadFromForm.php b/core/modules/file/tests/file_test/src/Form/FileTestSaveUploadFromForm.php
new file mode 100644
index 0000000..8aa39b4
--- /dev/null
+++ b/core/modules/file/tests/file_test/src/Form/FileTestSaveUploadFromForm.php
@@ -0,0 +1,124 @@
+<?php
+
+namespace Drupal\file_test\Form;
+
+use Drupal\Core\Form\FormInterface;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * File test form class.
+ */
+class FileTestSaveUploadFromForm implements FormInterface {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function getFormId() {
+    return '_file_test_save_upload_from_form';
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function buildForm(array $form, FormStateInterface $form_state) {
+    $form['file_test_upload'] = array(
+      '#type' => 'file',
+      '#title' => t('Upload a file'),
+    );
+    $form['file_test_replace'] = array(
+      '#type' => 'select',
+      '#title' => t('Replace existing image'),
+      '#options' => array(
+        FILE_EXISTS_RENAME => t('Appends number until name is unique'),
+        FILE_EXISTS_REPLACE => t('Replace the existing file'),
+        FILE_EXISTS_ERROR => t('Fail with an error'),
+      ),
+      '#default_value' => FILE_EXISTS_RENAME,
+    );
+    $form['file_subdir'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Subdirectory for test file'),
+      '#default_value' => '',
+    );
+
+    $form['extensions'] = array(
+      '#type' => 'textfield',
+      '#title' => t('Allowed extensions.'),
+      '#default_value' => '',
+    );
+
+    $form['allow_all_extensions'] = array(
+      '#type' => 'checkbox',
+      '#title' => t('Allow all extensions?'),
+      '#default_value' => FALSE,
+    );
+
+    $form['is_image_file'] = array(
+      '#type' => 'checkbox',
+      '#title' => t('Is this an image file?'),
+      '#default_value' => TRUE,
+    );
+
+    $form['submit'] = array(
+      '#type' => 'submit',
+      '#value' => t('Submit'),
+    );
+    return $form;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function validateForm(array &$form, FormStateInterface $form_state) {
+    // Process the upload and perform validation. Note: we're using the
+    // form value for the $replace parameter.
+    if (!$form_state->isValueEmpty('file_subdir')) {
+      $destination = 'temporary://' . $form_state->getValue('file_subdir');
+      file_prepare_directory($destination, FILE_CREATE_DIRECTORY);
+    }
+    else {
+      $destination = FALSE;
+    }
+
+    // Setup validators.
+    $validators = array();
+    if ($form_state->getValue('is_image_file')) {
+      $validators['file_validate_is_image'] = array();
+    }
+
+    if ($form_state->getValue('allow_all_extensions')) {
+      $validators['file_validate_extensions'] = array();
+    }
+    elseif (!$form_state->isValueEmpty('extensions')) {
+      $validators['file_validate_extensions'] = array($form_state->getValue('extensions'));
+    }
+
+    // The test for drupal_move_uploaded_file() triggering a warning is
+    // unavoidable. We're interested in what happens afterwards in
+    // file_save_upload().
+    if (\Drupal::state()->get('file_test.disable_error_collection')) {
+      define('SIMPLETEST_COLLECT_ERRORS', FALSE);
+    }
+
+    $form['file_test_upload']['#upload_validators'] = $validators;
+    $form['file_test_upload']['#upload_location'] = $destination;
+
+    $file = file_save_upload_from_form($form['file_test_upload'], $form_state, 0, $form_state->getValue('file_test_replace'));
+    if ($file) {
+      $form_state->setValue('file_test_upload', $file);
+      drupal_set_message(t('File @filepath was uploaded.', array('@filepath' => $file->getFileUri())));
+      drupal_set_message(t('File name is @filename.', array('@filename' => $file->getFilename())));
+      drupal_set_message(t('File MIME type is @mimetype.', array('@mimetype' => $file->getMimeType())));
+      drupal_set_message(t('You WIN!'));
+    }
+    elseif ($file === FALSE) {
+      drupal_set_message(t('Epic upload FAIL!'), 'error');
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function submitForm(array &$form, FormStateInterface $form_state) { }
+
+}
diff --git a/core/modules/system/src/Form/ThemeSettingsForm.php b/core/modules/system/src/Form/ThemeSettingsForm.php
index e7b11ea..5dbc411 100644
--- a/core/modules/system/src/Form/ThemeSettingsForm.php
+++ b/core/modules/system/src/Form/ThemeSettingsForm.php
@@ -212,7 +212,10 @@ public function buildForm(array $form, FormStateInterface $form_state, $theme =
         '#type' => 'file',
         '#title' => t('Upload logo image'),
         '#maxlength' => 40,
-        '#description' => t("If you don't have direct file access to the server, use this field to upload your logo.")
+        '#description' => t("If you don't have direct file access to the server, use this field to upload your logo."),
+        '#upload_validators' => array(
+          'file_validate_is_image' => array(),
+        ),
       );
     }
 
@@ -252,7 +255,12 @@ public function buildForm(array $form, FormStateInterface $form_state, $theme =
       $form['favicon']['settings']['favicon_upload'] = array(
         '#type' => 'file',
         '#title' => t('Upload favicon image'),
-        '#description' => t("If you don't have direct file access to the server, use this field to upload your shortcut icon.")
+        '#description' => t("If you don't have direct file access to the server, use this field to upload your shortcut icon."),
+        '#upload_validators' => array(
+          'file_validate_extensions' => array(
+            'ico png gif jpg jpeg apng svg',
+          ),
+        ),
       );
     }
 
@@ -355,38 +363,18 @@ public function validateForm(array &$form, FormStateInterface $form_state) {
     parent::validateForm($form, $form_state);
 
     if ($this->moduleHandler->moduleExists('file')) {
-      // Handle file uploads.
-      $validators = array('file_validate_is_image' => array());
-      $logo_upload_element = $form['logo']['settings']['logo_upload'];
-
       // Check for a new uploaded logo.
-      $file = file_save_upload_from_form($logo_upload_element, $form_state, 0);
-      if (isset($file)) {
-        // File upload was attempted.
-        if ($file) {
-          // Put the temporary file in form_values so we can save it on submit.
-          $form_state->setValue('logo_upload', $file);
-        }
-        else {
-          // File upload failed.
-          $form_state->setErrorByName($logo_upload_element, $this->t('The logo could not be uploaded.'));
-        }
+      $file = file_save_upload_from_form($form['logo']['settings']['logo_upload'], $form_state, 0);
+      if ($file) {
+        // Put the temporary file in form_values so we can save it on submit.
+        $form_state->setValue('logo_upload', $file);
       }
 
-      $validators = array('file_validate_extensions' => array('ico png gif jpg jpeg apng svg'));
-
       // Check for a new uploaded favicon.
       $file = file_save_upload_from_form($form['favicon']['settings']['favicon_upload'], $form_state, 0);
-      if (isset($file)) {
-        // File upload was attempted.
-        if ($file) {
-          // Put the temporary file in form_values so we can save it on submit.
-          $form_state->setValue('favicon_upload', $file);
-        }
-        else {
-          // File upload failed.
-          $form_state->setErrorByName('favicon_upload', $this->t('The favicon could not be uploaded.'));
-        }
+      if ($file) {
+        // Put the temporary file in form_values so we can save it on submit.
+        $form_state->setValue('favicon_upload', $file);
       }
 
       // When intending to use the default logo, unset the logo_path.