CVE-2025-54143: Sandboxed iframes could allow local downloads despite sandbox restrictions

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-08-19 · updated 2026-10-05
Weakness: CWE-693

Description

Sandboxed iframes on webpages could potentially allow downloads to the device, bypassing the expected sandbox restrictions declared on the parent page. This vulnerability was fixed in Firefox for iOS 141.

Affected products

Mozilla Firefox: before 141.0 — fixed in 141.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 141.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1912671
https://www.mozilla.org/security/advisories/mfsa2025-60/

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