CVE-2021-23956

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.0% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2021-02-26 · updated 2026-06-17

Description

An ambiguous file picker design could have confused users who intended to select and upload a single file into uploading a whole directory. This was addressed by adding a new prompt. This vulnerability affects Firefox < 85.

Affected products

Mozilla Firefox: before 85.0 — fixed in 85.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 85.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1338637
https://www.mozilla.org/security/advisories/mfsa2021-03/
https://bugzilla.mozilla.org/show_bug.cgi?id=1338637
https://www.mozilla.org/security/advisories/mfsa2021-03/

Get alerted when CVE-2021-23956 or the next vulnerability affects your stack