What about SPAs tho? Some of the state is in the URL, and as the user fills the form, you might push state to undo last step of the form. Does this mean that in this context the user gets thrown to about:blank? That would break tons of websites.
replyI use all kinds of web apps and forms and have no issues with undo or other features. And the changes Firefox made to prevent malicious JS changing browser history were done in 2016. I don't think it has anything to do with undo within a page and I wouldn't expect the browser back button to replicate undo (ctrl + z).
replyAs for my small UserScript, it has nothing to do with browser history state. It simply forces web site JS to share certain key strokes with my browser, add-ons and scripts instead of swallowing them (and it's easy to include/exclude any site or page).