This issue can be caused by an extension that isn't working properly.

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do not click the Reset button on the Safe mode start window or otherwise make changes.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Support for enablePrivilege has been removed in Firefox (Bug 546848), so it is no longer possible to get special elevated privileges by using this method.

Extensions do not need to use this (they already run code with proper privileges) and if web page use this then they will have to use other ways get what they want like providing a Firefox extension.

Question owner

The problem still happens in Safe Mode, it is not being caused by an extension or theme nor other possible causes like plugins or changes made to Firefox preference settings, which are not disabled in Safe Mode.

Are you able to determine the cause of this error message?

Is it caused by a (local or internet) page that are opening on startup if it isn't an extension?

Create a new profile as a test to check if your current profile is causing the problems.

See "Creating a profile":

• https://support.mozilla.org/kb/profile-manager-create-and-remove-firefox-profiles
• http://kb.mozillazine.org/Standard_diagnostic_-_Firefox#Profile_issues

If the new profile works then you can transfer some files from an existing profile to the new profile, but be careful not to copy corrupted files.

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox

Question owner

yes, the error message comes from a javascript line like this:

netscape.security.PrivilegeManager.enablePrivilege('UniversalXPConnect');

Is it caused by a local and/or internet page opened with firefox 17.x.

Anyway I found a workaround here:

https://developer.mozilla.org/en-US/docs/Site_Compatibility_for_Firefox_17#Security

thanks

OK - this just started happening to me today, even though I've been using FF19 since it was available. I'm not sure i understand what this means, and whether I really need to do anything. It has only popped up when I have clicked an email link and it has opened FF (my default browser). Does this mean it has to do with the site being opened or something else? If I don't do anything but click OK and close it am I doing harm somehow? So far it is a minor inconvenience, but since I don't understand it I need more info - or at least reassurance that it is harmless.

On Windows this issue can be caused by the AVG Security Toolbar or another AVG extension.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes