CVE-2025-3859: Firefox Focus elide URL allows address bar spoofing

Severity: medium (CVSS 6.1 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: 2025-04-30 · updated 2026-06-17
Weakness: CWE-601

Description

Websites directing users to long URLs that caused eliding to occur in the location view could leverage the truncating behavior to potentially trick users into thinking they were on a different webpage. This vulnerability was fixed in Focus 138.

Affected products

Mozilla Focus for iOS: before 138.0 — fixed in 138.0

How to fix

Upgrade to a fixed version: Mozilla Focus for iOS 138.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1951533
https://www.mozilla.org/security/advisories/mfsa2025-33/

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