What’s Vulnerable › Vulnerabilities

CVE-2020-15655

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-08-10 · updated 2026-06-17

Description

A redirected HTTP request which is observed or modified through a web extension could bypass existing CORS checks, leading to potential disclosure of cross-origin information. This vulnerability affects Firefox ESR < 78.1, Firefox < 79, and Thunderbird < 78.1.

Affected products

• Canonical Ubuntu Linux: 16.04, 18.04, 20.04
• Mozilla Firefox: before 79.0 — fixed in 79.0
• Mozilla Firefox ESR: before 78.1 — fixed in 78.1
• Mozilla Thunderbird: before 78.1 — fixed in 78.1
• openSUSE Leap: 15.2

How to fix

Upgrade to a fixed version: Mozilla Firefox 79.0; Mozilla Firefox ESR 78.1; Mozilla Thunderbird 78.1. Check the vendor advisory for mitigations.

References

• http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00025.html
• https://bugzilla.mozilla.org/show_bug.cgi?id=1645204
• https://usn.ubuntu.com/4443-1/
• https://www.mozilla.org/security/advisories/mfsa2020-30/
• https://www.mozilla.org/security/advisories/mfsa2020-32/
• https://www.mozilla.org/security/advisories/mfsa2020-33/
• http://lists.opensuse.org/opensuse-security-announce/2020-08/msg00025.html
• https://bugzilla.mozilla.org/show_bug.cgi?id=1645204
• https://usn.ubuntu.com/4443-1/
• https://www.mozilla.org/security/advisories/mfsa2020-30/
• https://www.mozilla.org/security/advisories/mfsa2020-32/
• https://www.mozilla.org/security/advisories/mfsa2020-33/

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