CVE-2020-26973 Cross-site scripting in Firefox
A flaw in the CSS Sanitizer allows attackers to bypass security checks, potentially enabling cross-site scripting attacks in Firefox and Thunderbird.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2020-26973?
CVE-2020-26973 is a high-severity cross-site scripting vulnerability in Mozilla Firefox, published on 7 Jan 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Certain input to the CSS Sanitizer confused it, resulting in incorrect components being removed. This could have been used as a sanitizer bypass. This vulnerability affects Firefox < 84, Thunderbird < 78.6, and Firefox ESR < 78.6.
Which versions are affected by CVE-2020-26973?
It affects 3 products.
Products include Mozilla Firefox, Mozilla Firefox Esr, Mozilla Thunderbird.
How do I fix CVE-2020-26973?
Upgrade to a fixed version.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2020-26973 being exploited?
There is no known exploitation of CVE-2020-26973 in the wild and no public exploit code.
Other vulnerabilities in Mozilla Firefox
Sources
Also known as DEBIAN-CVE-2020-26973, GHSA-7p7r-8rqq-6xf9, UBUNTU-CVE-2020-26973.