You were seeing issues from the graphics driver, not Firefox.

Any memory allocation failing within the browser forces an instant crash unless the callsite explicitly opts in to handling the allocation failure.

"Check malloc failure" is an opt-out feature in browsers, not opt-in. It's the same in Chromium. Failing to check would cause too many security issues. (One more reason new stuff tends to prefer Rust, etc)

Thanks for the info! I guess it also makes sense as I realized after posting, if it did use the result of malloc unused it should crash immediately due to references into the zero page segment, thus can't have been what I saw.