CVE-2020-15664: Mozilla Firefox

Medium severity, CVSS 6.5. EPSS: 1.4% chance of exploitation in the next 30 days.

By holding a reference to the eval() function from an about:blank window, a malicious webpage could have gained access to the InstallTrigger object which would allow them to prompt the user to install an extension. Combined with user confusion, this could result in an unintended or malicious extension being installed. This vulnerability affects Firefox < 80, Thunderbird < 78.2, Thunderbird < 68.12, Firefox ESR < 68.12, Firefox ESR < 78.2, and Firefox for Android < 80.

Affected products

• Mozilla Firefox: before 80.0 (fixed in 80.0); from 78.0, before 78.2 (fixed in 78.2)
• Mozilla Firefox ESR: before 68.12 (fixed in 68.12)
• Mozilla Firefox Mobile: before 80.0 (fixed in 80.0)
• Mozilla Thunderbird: before 68.12 (fixed in 68.12); from 78.0, before 78.2 (fixed in 78.2)

Published 2020-10-01. Last modified 2026-08-19.