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.

• Bug 546848 - Remove support for enablePrivilege

If a web page is using this then they will have to use other ways get what they want like providing a Firefox extension.

This issue can be caused by an extension that isn't working properly and needs to be updated.

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

I got rid of it using these steps :

1. In the Firefox dropdown list, select Add-Ons 2. Click on Add-Ons and select Extensions

Deleted AVG Toolbar. No more error message!