server problems 403, file not found

[shawn_a]

I have never encountered a filter that does this, but it makes sense.
It would be great if you could find out which mod_sec rule it is, they have numbers. And usually some log logs the hits in more detail.

If your host allows you can do some htaccess fu and disable specific rules or all etc.

Maybe enabling entities setting in ckeditor will help, i think it does encoding on them.

And I would create that 403 file to quiet your logs a bit.