CVE-2020-26958

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    CVE-2020-26958

    Published: 9 Dec 2020Last Modified: 16 Apr 2026

    Summary:

    Details: Firefox did not block execution of scripts with incorrect MIME types when the response was intercepted and cached through a ServiceWorker. This could lead to a cross-site script inclusion vulnerability, or a Content Security Policy bypass. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.

    References: https://www.mozilla.org/security/advisories/mfsa2020-50/, https://www.mozilla.org/security/advisories/mfsa2020-51/, https://www.mozilla.org/security/advisories/mfsa2020-52/, https://bugzilla.mozilla.org/show_bug.cgi?id=1669355

    Affected packages

    Package

    Name:

    Purl:

    Affected ranges

    Type: N/A

    Events:

    Introduced- None
    Fixed -None

    Affected versions

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High
    CVE-2020-26958 | CVE-DB