alt Hacker News> Firefox bugs are bugs in Firefox. (I also keep experiencing the stuck menu bug, but again, Firefox bug.)
Glitches in context menus could theoretically be just Firefox bugs. Glitches in the global menu bar can't be just Firefox bugs. Those pixels don't belong to Firefox. It shouldn't be possible for an application to cause the OS to lose track of which menu the user has open in the global menu bar. Even if Firefox is buggy here (quite likely), there's clearly a deficiency in the OS itself, too.
The menus, and what happens when you open/close them, do belong to Firefox. Cocoa gives apps a fair amount of power here. In Firefox's case, the issue is likely because each window specifies its own independent set of menu bar menus - very un-macOS - and it handles that by destroying and recreating the global menu bar every time you switch windows. The stuck menu bug seems to happen when a window is opened or closed, so my guess would be that something about the destroy-and-recreate routine is broken on macOS 27.