Table of Contents
What Should Windows 7 and 8.1 Users Do Now That Firefox 115 ESR Support Is Ending?
Firefox 115.32.1esr on Windows 7/8.1: What You Need to Know
Firefox 115.32.1esr is the most recent security release of Mozilla Firefox for Windows 7 and Windows 8.1 users, and it addresses a critical vulnerability. If you are still running either of these operating systems, this update is not optional — it is essential.
The Security Fix: CVE-2026-2447
The update closes a “High Impact” heap buffer overflow vulnerability, tracked as CVE-2026-2447, found inside libvpx — the video codec library used by the browser. A heap buffer overflow flaw allows malicious code to overwrite memory, potentially giving an attacker control over your system during normal browsing. The following software versions are confirmed affected and have since been patched:
- Firefox versions below 147.0.4
- Firefox ESR versions below 140.7.1
- Firefox ESR versions below 115.32.1
- Thunderbird versions below 140.7.2
- Thunderbird versions below 147.0.2
If you use any of these, updating immediately is the right move.
Is 115.32.1esr the Final Version?
Almost certainly, yes — but one more release is on the way. According to Mozilla’s support forum, Firefox 115.33.0esr is planned for release around February 24, 2026, and is expected to be the absolute last update for Windows 7 and 8.1. Mozilla’s official support page confirms that updates through the ESR channel will continue only until end of February 2026, after which no further security patches will be delivered to these platforms.
A Long History of Extended Support
Mozilla originally planned to end Firefox 115 ESR support in September 2024. Given that roughly 6.7% of all Firefox users were still on Windows 7 at that time, Mozilla chose to extend support — first into 2025, and then again. On September 4, 2025, Mozilla officially announced it would extend the Firefox 115 ESR branch through March 2026. That extension period is now drawing to a close.
What to Do After End-of-Life
Once Firefox 115 ESR reaches end-of-life, running it on Windows 7 or 8.1 becomes a security risk with no remediation path. Your practical options are:
- Upgrade your operating system to Windows 10 or 11 to continue receiving modern Firefox updates
- Use the r3dfox fork, a community-maintained Firefox fork available on GitHub that continues to support Windows 7 — a viable stopgap for users who cannot upgrade their hardware
- Switch to a lighter alternative browser that still maintains Windows 7 compatibility, such as Pale Moon or Basilisk
The r3dfox option, in particular, is worth exploring if a full OS upgrade is not immediately feasible. It is actively maintained and brings a more current browsing engine to legacy hardware.
The Bottom Line
Firefox 115.32.1esr is a critical patch you should apply right now. With Firefox 115.33.0esr as the expected final release arriving around February 24, 2026, and end-of-life confirmed shortly after, the window to plan your transition is narrow. Whether that means upgrading your OS or switching to a fork like r3dfox, acting before support expires keeps your system protected.