Question 1

What is the EOL Risk Score for Firefox 91?

Accepted Answer

Firefox 91 has an EOL Risk Score™ of 60 out of 100, placing it in the High risk band. The score is calculated from four factors: EOL Recency (40/40), Attack Surface (10/30), CISA KEV Exposure (0/20), and Extended Support Availability (10/10).

Question 2

Is Firefox 91 still supported?

Accepted Answer

Firefox 91 is no longer supported — it has passed its end of life date (September 20, 2022). No further security patches will be issued. Upgrade to a supported version or obtain extended lifecycle support.

Question 3

When does Firefox 91 reach end of life?

Accepted Answer

Firefox 91 reached (or will reach) end of life on September 20, 2022. After this date, no security patches or bug fixes are issued by the vendor.

Question 4

What are the security risks of running Firefox 91 after end of life?

Accepted Answer

After end of life, Firefox 91 no longer receives security patches. Any newly discovered CVEs remain unpatched indefinitely. Organizations running EOL software also face compliance violations under SOC 2, PCI DSS, HIPAA, and ISO 27001, which require use of supported software versions.