Mozilla has banned YouTube Unblocker from its add-on library after users complained that the software appeared to be misbehaving.
Softpedia reported that Avast anti-virus caught YouTube Unblocker trying to install malware on a user’s machine.
It did this by altering the browser’s security settings through installing a new user.js configuration file.
The new configuration file disabled Firefox’s add-on signing feature, which prevents the browser from installing add-ons that haven’t been tested and signed by Mozilla.
After turning off add-on signing, YouTube Unblocker tried to install an add-on called Adblock Converter – which Avast flagged as malware.
This add-on did not appear in Firefox’s standard add-ons page, and it re-enabled itself after being disabled in Safe Mode.
Mozilla has now removed YouTube Unblocker from its add-on portal, adding that it received similar reports about the software in June 2015.