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    CVE-2026-91123

    Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the iframe src traversal guard did not treat literal backslashes as path separators after decoded dot segments. A crafted source could therefore pass an allowed_iframes subpath check while browser URL normalization moved the iframe outside the intended allowed path. The resulting iframe could load content from a location that the administrator did not allow. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

    Published:Sep 24, 2026
    Last Modified:Sep 24, 2026
    EPS:Sep 24, 2026
    EPSS Score:
    CVSS Score:7.2

    Affected Products

    Vendor
    Discourse
    Product
    Discourse

    Exploits

    No exploit reference

    Related CVEs

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    CVE-2026-91157 (CVSS 7.5) — Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9, sites wi…
    CVE-2026-91156 (CVSS 7.5) — Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9, MessageB…
    CVE-2026-91159 (CVSS 7.7) — Discourse is an open-source discussion platform. Prior to 2026.9.0, 2026.8.1, 2026.7.3, and 2026.1.9, oEmbed p…
    CVE-2026-91119 (CVSS 6.4) — Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the topi…
    CVE-2026-91121 (CVSS 5) — Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, attacker…
    CVE-2026-91120 (CVSS 5.4) — Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, provider…
    CVE-2026-91132 (CVSS 4.3) — Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, sites us…
    CVE-2026-91122 (CVSS 8.7) — Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the vide…
    CVE-2026-91133 (CVSS 6.5) — Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, authenti…

    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