CVE-2019-9803

The Upgrade-Insecure-Requests (UIR) specification states that if UIR is enabled through Content Security Policy (CSP), navigation to a same-origin URL must be upgraded to HTTPS. Firefox will incorrectly navigate to an HTTP URL rather than perform the security upgrade requested by the CSP in some circumstances, allowing for potential man-in-the-middle attacks on the linked resources. This vulnerability affects Firefox < 66.

• CWE-346

• https://bugzilla.mozilla.org/show_bug.cgi?id=1437009Issue Tracking, Vendor Advisory
• https://bugzilla.mozilla.org/show_bug.cgi?id=1515863Issue Tracking, Permissions Required, Vendor Advisory
• https://w3c.github.io/webappsec-upgrade-insecure-requests/Third Party Advisory
• https://www.mozilla.org/security/advisories/mfsa2019-07/Vendor Advisory
• https://bugzilla.mozilla.org/show_bug.cgi?id=1437009Issue Tracking, Vendor Advisory
• https://bugzilla.mozilla.org/show_bug.cgi?id=1515863Issue Tracking, Permissions Required, Vendor Advisory
• https://w3c.github.io/webappsec-upgrade-insecure-requests/Third Party Advisory
• https://www.mozilla.org/security/advisories/mfsa2019-07/Vendor Advisory

Published

Apr 26, 2019

Last Modified

Jun 17, 2026

Status

Modified

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