Categories: Security

Rapidly Leveling up Firefox Security

At Mozilla, we believe in an open web that is safe to use. To that end, we improve and maintain the security of people using Firefox around the world. This includes a solid track record of responding to security bugs in the wild, especially with bug bounty programs such as Pwn2Own. As soon as we discover a critical security issue in Firefox, we plan and ship a rapid fix. This post describes how we recently fixed an exploit discovered at Pwn2Own in less than 21 hours, a success only made possible through the collaborative and well-coordinated efforts of a global cross-functional team of release and QA engineers, security experts, and other stakeholders.

A Bit Of Context

Pwn2Own is an annual computer hacking contest where participants aim to find security vulnerabilities in major software such as browsers. Two weeks ago, this event took place in Vancouver, Canada, where participants investigated everything from Chrome, Firefox, and Safari to MS Word and even the code currently running on your car. Without getting into the technical details of the exploit here, this blog post will describe how Mozilla quickly responds to and ships updated builds for exploits found during Pwn2Own.

To give you a sense of scale, Firefox is a massive piece of software: 30 million+ lines of code, six platforms (Windows 32 & 64bit, GNU/Linux 32 & 64bit, Mac OS X and Android), 90 languages, plus installers, updaters, etc. Releasing such a beast involves coordination across many cross-functional teams spanning the entire globe.

The timing of the Pwn2Own event is known weeks beforehand, so Mozilla is always ready when it rolls around! The Firefox train release calendar takes into consideration the timing of Pwn2Own. We try not to ship a new version of Firefox to end users on the release channel on the same day as Pwn2Own to hopefully avoid multiple updates close together. This also means that we are prepared to ship a patched version of Firefox as soon as we know what vulnerabilities were discovered if any at all.

So What Happened?

The specific exploit disclosed at Pwn2Own consisted of two bugs, a necessity when typical web content is rendered inside of a proverbial browser sandbox: These two sophisticated exploits took an admirable amount of effort to reveal and leverage. Nevertheless, as soon as it was discovered, Mozilla engineers got to work, shipping a new release within 21 hours! We certainly weren’t the only browser “pwned”, but we were the first of all, to patch our vulnerability. That’s right: before you knew about this exploit, we had already protected you from it.

As scary as this might sound, Sandbox Escapes, like many web browser exploits, are an issue common to all browsers, thanks to the evolving nature of the internet. Firefox developers are always eager to find and resolve these security issues as quickly as possible to ensure our users stay safe. We do this continuously by shipping new mitigations like win32k lockdown, site isolation, investing in security fuzzing, and promoting bug bounties for similar escapes. In the interest of openness and transparency, we also continuously invite and reward security researchers who share their newest attacks, which helps us keep our product safe even when there isn’t a Pwn2Own to participate in.

Related Resources

If you’re interested in learning more about Mozilla’s security initiatives or Firefox security, here are some resources to help you get started:

Mozilla Security
Mozilla Security Blog
Bug Bounty Program
Mozilla Security playlist on YouTube

Furthermore, if you want to kickstart your own security research in Firefox, we invite you to follow our deeply technical blog at Attack & Defense – Firefox Security Internals for Engineers, Researchers, and Bounty Hunters .

Past Pwn2Own Blog: