Today I was checking something about CKFinder and I've realized that the Upload button doesn't work in the latest beta of Firefox 3.6.
That's strange and quite important as lots of people will be using it as soon as it is released, so I dug into the code to find out the problem. After tracing the differences in the execution of 3.5 and 3.6 I've finally found that when an iframe is created it finish the initialization by checking for document.readyState to avoid problems using an unfinished document in IE, and now that code was triggered also by Firefox 3.6
The fact that Firefox includes a property that was previously supported by IE (and IIRC also Opera and Webkit) shouldn't break anything, that code path uses the document.onreadystatechange to properly listen for the change of state and finish the initialization.
The real problem is that such event hasn't been added to Firefox, so the code never executes!
Everything was OK without support for document.readyState, but now they have added it without including the document.onreadystatechange, so things might get broken due to this big oversight. I suggest all of you to review your code and check for the usage of this event (not to be confused with XHR.onreadystatechange) because Firefox 3.6 might be a real pain for you if you don't patch your code it in due time.
Mozilla guys: thank you for bringing us this extra work.