What does the update window look like? This is the official plugin update site: https://www.mozilla.org/plugincheck/ Is that it, or something else? What you're seeing may be generated by an add-on. Try disabling ALL nonessential or unrecognized add-ons on these two tabs: orange Firefox button (or Tools menu) > Add-ons > Plugins category<br> orange Firefox button (or Tools menu) > Add-ons > Extensions category Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step. If you would like comments on whether any of your extensions look untrustworthy, you can extract a list from the Troubleshooting Information page. Either: * Help > Troubleshooting Information * type or paste about:support in the address bar and press Enter In the upper left corner is a button to "Copy text to clipboard". When pasting into a reply, you'll see a lot of preference information below the extensions list. You can delete that lower part if you don't want comments on those.