Mozilla admits Firefox add-ons contained Trojan code

Graham Cluley
Graham Cluley
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Mozilla has issued a warning that two add-ons available from AMO (, the Mozilla Add-ons website) were infected by malicious code capable of infecting Windows computers.

According to a security notice on AMO’s blog, the Master Filer add-on was infected by the LdPinch password-stealing Trojan, and Sothink Web Video Downloader version 4.0 was infected by a version of the Bifrose backdoor Trojan horse. (Update: Mozilla reports that Sothink Web Video Downloader is not infected after all).

Judging by the statement on the Mozilla Add-ons blog, a fair few people could have found that their Windows computers were infected:

Master Filer was downloaded approximately 600 times between…

Read more in my article on the Naked Security website.

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Graham Cluley is a veteran of the cybersecurity industry, having worked for a number of security companies since the early 1990s when he wrote the first ever version of Dr Solomon's Anti-Virus Toolkit for Windows. Now an independent analyst, he regularly makes media appearances and is an international public speaker on the topic of cybersecurity, hackers, and online privacy. Follow him on Twitter, Mastodon, Threads, Bluesky, or drop him an email.