CVE-2026-0887: Clickjacking issue, information disclosure in the PDF Viewer component

Severity: medium (CVSS 4.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-01-13 · updated 2026-06-17
Weakness: CWE-497

Description

Clickjacking issue, information disclosure in the PDF Viewer component. This vulnerability was fixed in Firefox 147, Firefox ESR 140.7, Thunderbird 147, and Thunderbird 140.7.

Affected products

Mozilla Firefox: before 140.7.0; before 147.0 — fixed in 140.7.0, 147.0
Mozilla Thunderbird: before 140.7.0; before 147.0 — fixed in 140.7.0, 147.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 140.7.0, 147.0; Mozilla Thunderbird 140.7.0, 147.0. Check the vendor advisory for mitigations.

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2006500
https://www.mozilla.org/security/advisories/mfsa2026-01/
https://www.mozilla.org/security/advisories/mfsa2026-03/
https://www.mozilla.org/security/advisories/mfsa2026-04/
https://www.mozilla.org/security/advisories/mfsa2026-05/

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