You have 4 days to update Firefox before everything breaks

On March 14, 2025, a root certificate used to verify signed content and add-ons for Firefox, Thunderbird, and other Mozilla projects expired. The expiration of this certificate will cause problems for Firefox users unless they update to version 128 (or ESR 115.13+). This includes versions for Linux, MacOS, Windows, Android, and iOS — in other words, all platforms.

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Without updating, all features that rely on remote updates will cease to function, all add-ons will be automatically disabled, and DRM-protected content will stop playing. In addition, all systems dependent on content verification could stop functioning as expected.

The web browser itself will continue to work, but much of what you do with the browser will be broken.

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This means every Firefox user around the world must update to the latest version; otherwise, they’ll find out the hard way that this upgrade isn’t optional.

What is a root certificate?

A root certificate is used to verify the authenticity of websites, add-ons, and software updates. Without a root certificate in place, your browser cannot verify these items, and you could wind up with malicious software on your hands.

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Root certificates are crucial for the following reasons:

• Top-level validation: When a website or application requests a digital certificate from an intermediate certificate authority, it can be validated by checking the signature against the root certificate.
• Trusted certificates: When you visit a website, your browser checks that each certificate in the chain is signed by a trusted root certificate.
• Security chain: Every certificate has an issuer that points to a certificate higher in the hierarchy, which forms a chain of trust from the website back to the root certificate.

How to upgrade Firefox

First off, you need to do this ASAP. How you update will depend on the operating system. First, check to see which version you’re using by clicking the menu button in the upper-right corner and then selecting Help > About Firefox. In the resulting pop-up, you should see the version number listed. If it’s less than 128, you need to update.

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To update, visit the Firefox download page and download the installer for your OS. In most cases, you just double-click the installer file and walk through the installation wizard. For Linux, use your default package manager. For Android and iOS, upgrade through their respective app stores.

Don’t consider this a warning; rather, think of it as an imperative. If you use Firefox, do this now; otherwise, you’ll find yourself with a browser that no longer functions.

You can read more about this from the official Mozilla announcement.

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