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"Another program on your computer would like to modify Firefox with the following add-on" - how do I allow extensions?


I cannot get extensions to run or enable, nor does the browser remember my preference.

For example, after I install or Enable an extension, when I restart Firefox I get a tab for every extension that forces me to check "Allow this installation" after the prompt "Another program on your computer would like to modify Firefox with the following add-on".

Moreover, when I click 'Options' on an installed extension, Firefox freezes permanently.

Note that I DO NOT have any extensions.* files in my Profile folder, nor do they appear.

I am trying to get MozRepl running. I am able to install it, but the menu option does not get added in the 'Tools' menu. Moreover none of the installed extensions are able to add to the menu.

I've tried every solution in the following links

https://support.mozilla.org/en-US/questions/929335 http://kb.mozillazine.org/Preferences_not_saved https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save

I have made the Profiles\ folder and all subfolders Read-only, including the files.

I have tried the "Reset Firefox to its default state".

I have tried uninstalling (including removing all profiles/data) and re-installing Firefox, and I get the same issues.

My operating system is Windows 7 and I have McAfee SiteAdvisor Enterprise Plus and McAfee VirusScan Enterprise + AntiSpyware Enterprise.

Additional System Details


  • User Agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.64 Safari/537.11

More Information

  • Top 10 Contributor
  • Moderator
10755 solutions 96800 answers

Check that Firefox isn't set to run as Administrator.

Right-click the Firefox desktop shortcut and choose "Properties".

Make sure that all items are deselected in the "Compatibility" tab of the Properties window.

  • Privilege Level: "Run this program as Administrator" should not be selected
  • "Run this program in compatibility mode for:" should not be selected

Also check the Properties of the firefox.exe program in the Firefox program folder (C:\Program Files\Mozilla Firefox\).