Copy-pasting within Ckeditor adds   for every space

I seem to have encountered this issue as well (though I use WYSIWYG). I suspect this is a variation of this ckeditor issue which is reported to impact webkit browsers.

See Ckeditor (libary) issue: [Chrome 23]   is created

This is new erroneous behavior in CKEditor 4 using Chrome 23, Win7 x64. Steps to reproduce:

go to official demo page of CKEditor 4, wysiwyg mode
delete any character using backspace or delete key
immediately type a space just by plain spacebar
see the source - nbsp is created instead of common space char

@morningtime - any chance to check this on a vanilla installation of Drupal + CKEditor module? It looks like certain configuration is triggering it... unless you're able to reproduce it at http://ckeditor.com/demo as well?
If yes, let me know what OS and browser are you using.

Updated issue summary.

If the original issue was an instance of #2, that got fixed in version 4.2.3 of the ckeditor library a few weeks back.

Their fix is actually a work around for some browser bugs which might ultimately be the root of the problem.
​https://bugs.webkit.org/show_bug.cgi?id=123163
​https://code.google.com/p/chromium/issues/detail?id=310149

I have the same problem and am using ckeditor 4.3.4. copy and paste causes all spaces to be converted. This happens regardless of if use html entities is turned on or not under advanced settings. I can't replicate it on ckeditor demo. It doesn't however happen if you use paste from word option.

http://docs.ckeditor.com/#!/api/CKEDITOR.config-cfg-basicEntities

config.basicEntities = false;

Setting that does stop it however it does also have security implications. I believe it has something to do with the text being utf-8. Oh and if you copy utf-8 text (ie from your ckeditor) and paste it into the demo the same problem occurs. So it does seem to be a ckeditor issue.

Orthographic corrector SCAYT (Spell Check As You Type) of CKE is the cause of this issue on my installation. I removed it and no more   !

Could also try https://www.drupal.org/project/ckeditor_paragraph_paste_fix

This seems to be a browser issue, not a ckeditor issue. I don't remember where I read it, but it appears that TinyMCE has the same problem in chrome and safari (webkit).