MyBB Community Forums

I posted a javascript doc in code tags here
https://python-forum.io/Thread-indentati...5#pid34465

from ckeditor plugin for mybb
https://community.mybb.com/mods.php?acti...oad&pid=73

location of file in plugin as i dont dare to post it here now
/jscripts/ckeditor/ckeditor.js

as soon as i posted that, the thread froze and my browser crashes when i load that thread. How can i delete the last post and why did this happen?

I tried numerous browser and get the same.
I tried to disable javascript on my website, to try to be able to not have it crash...and it doesnt. But the delete post checkbox doesnt get recognized as checked to delete if i have javascript disabled.

EDIT:
fixed the problem for now. I was able to edit the post to remove the content with javascript disabled for my site, then renabled javascript, and its normal now.

Why does this do that? Isnt this a vulnerability for javascript injection?

Please can you provide the code snippet in a pastebin so that we can attempt to replicate this issue?
A pastebin can be started here: https://pastebin.com

i copied and paste this in code tags on my mybb forum (the entire file) 
https://github.com/martec/Rin-Editor/blo...keditor.js