diff --git a/core/lib/Drupal/Component/Utility/UrlHelper.php b/core/lib/Drupal/Component/Utility/UrlHelper.php
index 77bac32bdb..6782d6bce4 100644
--- a/core/lib/Drupal/Component/Utility/UrlHelper.php
+++ b/core/lib/Drupal/Component/Utility/UrlHelper.php
@@ -174,7 +174,7 @@ public static function parse($url) {
       // Strip the leading slash that was just added.
       $options['path'] = substr($parts['path'], 1);
       if (isset($parts['query'])) {
-        parse_str($parts['query'], $options['query']);
+        $options['query'] = static::parseQueryString($parts['query']);
       }
       if (isset($parts['fragment'])) {
         $options['fragment'] = $parts['fragment'];
@@ -185,30 +185,36 @@ public static function parse($url) {
   }
 
   /**
-   * Convert an url query string to an array.
+   * A wrapper for parse_str() that restores original parameter names.
    *
-   * The parse_str method contains an issue with query parameter names
-   * containing a dot. Having a dot in a query parameter name is valid, so
-   * we hex encode the parameter names to work around this.
+   * The parse_str() function can be used to set variables in the current scope,
+   * although this is deprecated. Because variables in PHP cannot have periods
+   * and spaces in their names, parse_str() converts them to underscores. This
+   * breaks external links and front end libraries that require specific
+   * parameter names.
    *
-   * @param string $query_string
-   *   The url parameters as a string.
+   * @param string $query
+   *   A query string to parse.
    *
    * @return array
-   *   The url parameters as an array.
-   *
-   * @see https://www.drupal.org/project/drupal/issues/2984272
+   *   The result of parse_str() with original parameter names restored.
    */
-  public static function parseQueryString($query_string = '') {
-    $query_options = [];
-    if ($query_string) {
-      $encoded_string = preg_replace_callback('/(?:^|(?<=&))[^=[]+/', function ($match) {
-        return bin2hex(urldecode($match[0]));
-      }, $query_string);
-      parse_str($encoded_string, $query_array);
-      $query_options = array_combine(array_map('hex2bin', array_keys($query_array)), $query_array);
+  public static function parseQueryString($query) {
+    // Create an array to map parsed parameter names to original names.
+    $names = [];
+    foreach (explode('&', $query) as $param) {
+      list($name) = explode('=', $param, 2);
+      parse_str($name, $parsed);
+      $names[key($parsed)] = $name;
+    }
+    // Parse the query string.
+    parse_str($query, $query);
+    // Replaced changed parameter names with original names.
+    foreach (array_diff($names, array_keys($query)) as $parsed => $name) {
+      $query[$name] = $query[$parsed];
+      unset($query[$parsed]);
     }
-    return $query_options;
+    return $query;
   }
 
   /**