You're either using CSS customizations (via userChrome.css) or extensions that break your menu. Similar report here, with no answers from the reporter: https://www.reddit.com/r/firefox/comments/1hw67w5/firefox_update_broke_right_click_menu/ Are you using userChrome.css? Does it work if you start Firefox in [Troubleshoot mode](https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems#w_start-firefox-in-troubleshoot-mode)?
Bug 1940533 Comment 1 Edit History
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The most likely cause is CSS customizations (via userChrome.css) or extensions that break your menu. Similar report here, with no answers from the reporters: https://www.reddit.com/r/firefox/comments/1hw67w5/firefox_update_broke_right_click_menu/ Are you using userChrome.css? Does it work if you start Firefox in [Troubleshoot mode](https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems#w_start-firefox-in-troubleshoot-mode)?