What’s Vulnerable › Vulnerabilities

CVE-2021-29987

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-08-17 · updated 2026-06-17
• Weakness: CWE-307

Description

After requesting multiple permissions, and closing the first permission panel, subsequent permission panels will be displayed in a different position but still record a click in the default location, making it possible to trick a user into accepting a permission they did not want to. *This bug only affects Firefox on Linux. Other operating systems are unaffected.*. This vulnerability affects Firefox < 91 and Thunderbird < 91.

Affected products

• Mozilla Firefox: before 91.0 — fixed in 91.0
• Mozilla Thunderbird: before 91.0 — fixed in 91.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 91.0; Mozilla Thunderbird 91.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1716129
• https://security.gentoo.org/glsa/202202-03
• https://www.mozilla.org/security/advisories/mfsa2021-33/
• https://www.mozilla.org/security/advisories/mfsa2021-36/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1716129
• https://security.gentoo.org/glsa/202202-03
• https://www.mozilla.org/security/advisories/mfsa2021-33/
• https://www.mozilla.org/security/advisories/mfsa2021-36/

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