What’s Vulnerable › Vulnerabilities

CVE-2020-15658

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-08-10 · updated 2026-06-17
• Weakness: CWE-754

Description

The code for downloading files did not properly take care of special characters, which led to an attacker being able to cut off the file ending at an earlier position, leading to a different file type being downloaded than shown in the dialog. 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

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=1637745
• 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=1637745
• 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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