vulnerability
MFSA2021-15 Firefox: Security Vulnerabilities fixed in Firefox ESR 78.10 (CVE-2021-23999)
| Severity | CVSS | Published | Added | Modified |
|---|---|---|---|---|
| 7 | (AV:N/AC:M/Au:N/C:P/I:P/A:P) | Apr 19, 2021 | Apr 20, 2021 | Mar 27, 2026 |
Severity
7
CVSS
(AV:N/AC:M/Au:N/C:P/I:P/A:P)
Published
Apr 19, 2021
Added
Apr 20, 2021
Modified
Mar 27, 2026
Description
If a Blob URL was loaded through some unusual user interaction, it could have been loaded by the System Principal and granted additional privileges that should not be granted to web content. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.
Solution
mozilla-firefox-esr-upgrade-78_10
Rapid7 Labs
2026 Global Threat Landscape Report
The predictive window has collapsed. Exploitation follows disclosure in days. See how attackers are accelerating and how to stay ahead.