CVE-2020-12391

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2020-05-26 · updated 2026-06-17
Weakness: CWE-863

Description

Documents formed using data: URLs in an OBJECT element failed to inherit the CSP of the creating context. This allowed the execution of scripts that should have been blocked, albeit with a unique opaque origin. This vulnerability affects Firefox < 76.

Affected products

Mozilla Firefox: before 76.0 — fixed in 76.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 76.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1457100
https://www.mozilla.org/security/advisories/mfsa2020-16/
https://bugzilla.mozilla.org/show_bug.cgi?id=1457100
https://www.mozilla.org/security/advisories/mfsa2020-16/

Get alerted when CVE-2020-12391 or the next vulnerability affects your stack