We also deployed a system add-on named ‘Proxy Failover’ (ID: with additional mitigations that has been shipped to both current and older Firefox versions,” states Mozilla’s blog post. Ensuring these requests are completed successfully helps us deliver the latest important updates and protections to our users. “Starting with Firefox 91.1, Firefox now includes changes to fall back to direct connections when Firefox makes an important request (such as those for updates) via a proxy configuration that fails. If you are not, follow the update instructions to get the latest version of Firefox. If you’re using the up-to-date Firefox version 93, add-ons that misuse the proxy API are already blocked. And, to deter the possibility of any mischievous ones from popping up, Mozilla has temporarily suspended accepting extensions that make use of Firefox’s proxy API.Īt this time, Microsoft Defender appears to be the only antivirus solution detecting the add-ons.

Checking if you are affected How to remove these add-onsįortunately, the add-ons are no longer on the Firefox Add-ons store.

“The add-ons also had Mozilla’s domain in the paywall list which inadvertently also blocked browser updates,” states the same report. These add-ons interfered with Firefox in a way that prevented users who had installed them from downloading updates, accessing updated blocklists, and updating remotely configured content,” explain Mozilla engineering managers Rachel Tublitz and Stuart Colville in a blog post.īoth ‘Bypass’ and ‘Bypass XM’ were seen to be in use by 455,000 Firefox users.Īdditional reporting by BleepingComputer revealed that the extensions were possibly “using a reverse proxy to bypass paywalled sites,” although Mozilla didn’t share any additional insights into the malicious nature of addons. “In early June, we discovered add-ons that were misusing the proxy API, which is used by add-ons to control how Firefox connects to the internet. The addons blocked access to the latest web browser updates, up-to-date access lists, and content: Mozilla has removed two Firefox extensions called ‘Bypass’ and ‘Bypass XM’ from the Add-ons store.īoth of these add-ons were caught abusing Firefox’s proxy API that enables developers to intercept web requests and determine whether and how to proxy them.

Firefox update