Hi all!
Even though this is not a CKEditor problem, it may affect CKEditor users so I post this.
I use CKEditor 3 as an editor for my university scholar journal CMS.
This week some of the editors pointed out that some ads were displaying on our new articles. After further investigation I noticed that some articles had, on the source code, a final hidden textarea that id itself as "adlesse_unifier_magic_element_id". Upon further searching I discovered that, according to other people experiencing the same issue, this was due to a malicous Safari extension (no idea which, I'm not on a Mac) which, once activated, would start adding this code to ALL your form submission. If you search online you'll find that when posting on a forum, you'll get the html stripped and converted, so you actually read the code, but when posting on CKEditor, this will end up covering your website content with ads!
Removing the string seem not enough to remove the ads... I'll post here when I find what I can do to avoid them!
update
Upon further searching, in the middel of my code there was hiding a script, at least in few of the affected files, so maybe the first time you open the file you add a textarea, if you re-edit it you'll get the malicious script
At least, this is what I could find...