CVE-2025-3033: Opening local .url files could lead to another file being opened

Severity: high (CVSS 7.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-04-01 · updated 2026-09-30
Weakness: CWE-73

Description

After selecting a malicious Windows `.url` shortcut from the local filesystem, an unexpected file could be uploaded. *This bug only affects Firefox on Windows. Other operating systems are unaffected.*. This vulnerability was fixed in Firefox 137 and Thunderbird 137.

Affected products

Mozilla Firefox: before 137.0 — fixed in 137.0
Mozilla Thunderbird: before 137.0 — fixed in 137.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 137.0; Mozilla Thunderbird 137.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1950056
https://www.mozilla.org/security/advisories/mfsa2025-20/
https://www.mozilla.org/security/advisories/mfsa2025-23/

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