Question 1

What is the EOL Risk Score for Firefox 159?

Accepted Answer

Firefox 159 has an EOL Risk Score™ of 55 out of 100, placing it in the High risk band. The score is calculated from four factors: EOL Recency (15/40), Attack Surface (10/30), CISA KEV Exposure (20/20), and Extended Support Availability (10/10).

Question 2

Is Firefox 159 still supported?

Accepted Answer

Firefox 159 is currently supported. End of life is scheduled for November 10, 2026. Plan your migration before that date to avoid security risk.

Question 3

When does Firefox 159 reach end of life?

Accepted Answer

Firefox 159 reached (or will reach) end of life on November 10, 2026. After this date, no security patches or bug fixes are issued by the vendor.

Question 4

What are the security risks of running Firefox 159 after end of life?

Accepted Answer

After end of life, Firefox 159 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.