XF 2.1 HTTP 400 error on image upload

[rfc0001]

Multiple users getting "Oops! We ran into some problems" error. In my own test, the console errors were:

• Failed to load resource: the server responded with a status of 400 ()
• editor-compiled.js?_v=d362c6aa:63 POST https://xyz.com/forum/attachments/upload?type=post&context[post_id]=95713&hash=f84d13ede901e6c1060ff822dc7df269 400

No errors in ACP.

Any thoughts on how to troubleshoot?

 

[rfc0001]

Disabled all add-ons and still able to repro

 

[rfc0001]

Seems to be happening with images that take a long time to upload (e.g. > 2 minutes), which obviously is an issue itself, but seems like they actually complete uploading successfully then get an error.

 

[rfc0001]

So, I didn't realize it but the image I am using is over my attachment limit size. Shouldn't I get an error stating this rather than just the "Oops! We ran into some problems" message? Seems like a bug if so.

 

[rfc0001]

I have a feeling this is due to post_max_size = upload_max_filesize in php.ini, in which case user doesn't get error that file exceeds max upload size. Fix would be set post_max_size = upload_max_filesize + 1.