What’s Vulnerable › Vulnerabilities

CVE-2019-11747

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-09-27 · updated 2026-06-17
• Weakness: CWE-665

Description

The "Forget about this site" feature in the History pane is intended to remove all saved user data that indicates a user has visited a site. This includes removing any HTTP Strict Transport Security (HSTS) settings received from sites that use it. Due to a bug, sites on the pre-load list also have their HSTS setting removed. On the next visit to that site if the user specifies an http: URL rather than secure https: they will not be protected by the pre-loaded HSTS setting. After that visit the site's HSTS setting will be restored. This vulnerability affects Firefox < 69 and Firefox ESR < 68.1.

Affected products

• Mozilla Firefox: before 69.0 — fixed in 69.0
• Mozilla Firefox ESR: before 68.1.0 — fixed in 68.1.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 69.0; Mozilla Firefox ESR 68.1.0. Check the vendor advisory for mitigations.

References

• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html
• https://bugzilla.mozilla.org/show_bug.cgi?id=1564481
• https://www.mozilla.org/security/advisories/mfsa2019-25/
• https://www.mozilla.org/security/advisories/mfsa2019-26/
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00011.html
• http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00017.html
• https://bugzilla.mozilla.org/show_bug.cgi?id=1564481
• https://www.mozilla.org/security/advisories/mfsa2019-25/
• https://www.mozilla.org/security/advisories/mfsa2019-26/

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