--- title: Mozilla pulls malicious Firefox extension description: Recently, the team behind Mozilla Firefox blocked a dangerous add-on for the popular browser, one that had accrued half a million users. canonical_url: https://www.acronis.com/en/tru/posts/mozilla-pulls-malicious-firefox-extension/ locale: en last_updated: 2026-10-27 --- * [Home](https://www.acronis.com/en/tru/) * [Articles](https://www.acronis.com/en/tru/posts/) * [Acronis Threat Research Unit](https://www.acronis.com/en/tru/authors/acronis-threat-research-unit/) 30 October 2021 # Mozilla pulls malicious Firefox extension Recently, the team behind Mozilla Firefox blocked a dangerous add-on for the popular browser, one that had accrued half a million users. Author: **[Acronis Threat Research Unit](https://www.acronis.com/en/tru/authors/acronis-threat-research-unit/)** [Video 1](https://www.youtube.com/watch?v=A4r2qi5pEYU) Recently, the team behind Mozilla Firefox blocked a dangerous add-on for the popular browser, one that had accrued half a million users. Usually browser add-ons enrich the user experience, but sometimes they can have hidden, malicious behaviors. This particular one misused Firefox's proxy API to block users from updating the browser, access updated blocklists, or updating remotely configured Firefox content. Regardless of the software or add-on in question, Acronis Cyber Protect recognizes malicious behavior and blocks it from executing, keeping your systems safe and ensuring that important patches can be successfully acquired. Related articles [The Gentlemen: A closer look at a not-so-gentle ransomware-as-a- service operation](https://www.acronis.com/en/tru/posts/the-gentlemen-a-closer-look-at-a-not-so-gentle-ransomware-as-a-service-operation/) [Acronis AI Copilot: Adoption is high and growing among MSPs](https://www.acronis.com/en/tru/posts/acronis-ai-copilot-adoption-is-high-and-growing-among-msps/) [Acronis Cyberthreats Update, October 2026](https://www.acronis.com/en/tru/posts/acronis-cyberthreats-update-october-2026/) [AI agents at work: What Acronis endpoint data reveals about MSP and SMB usage](https://www.acronis.com/en/tru/posts/ai-agents-at-work-what-acronis-endpoint-data-reveals-about-msp-and-smb-usage/)