Steps to replicate the issue (include links if applicable):
What happens?:
You can't undo it, and your browser will crash.
What should have happened instead?:
You can easily undo the edit.
Software version (skip for WMF-hosted wikis like Wikipedia):
Other information (browser name/version, screenshots, etc.):
Error: The text you have submitted is 19,849.629 kilobytes long, which is longer than the maximum of 2,048 kilobytes. It cannot be published.
Closing as invalid,
No matter the type of edit (new, using undo or rollback) is going to fail in different methods if its over the page size limit. The fact we have managed to create a 19MB page when 2MB is the limit is a separate issue.
As indicated in the page history, that's a test page for T270022. This genre of bug arose when the page size limit stopped being enforced by the database. I think we previously fixed how the Unicode characters are normalised for the purpose of the limit?