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Review reviewCritical

CVE-2026-53963

discourse

Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, a malicious second factor name on an attacker-controlled account was not escaped in the delete confirmation dialog, allowing stored cross-site scripting when an administrator impersonated that account. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

CVSS
9
EPSS
0.45%
36.9% percentile
CISA KEV
Not listed
Published
2026.07.10
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.45%
Technical severityCVSS 9

Vulnerability overview

Discourse is an open-source discussion platform. Prior to 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5, a malicious second factor name on an attacker-controlled account was not escaped in the delete confirmation dialog, allowing stored cross-site scripting when an administrator impersonated that account. This issue is fixed in versions 2026.6.0, 2026.5.1, 2026.4.2, and 2026.1.5.

Affected product and versions

Product
discourse
Affected versions
>= >= 2026.1.0-latest, < 2026.1.5, >= >= 2026.4.0-latest, < 2026.4.2, >= >= 2026.5.0-latest, < 2026.5.1, >= 2026.1.0 < 2026.1.5, >= 2026.4.0 < 2026.4.2, >= 2026.5.0 < 2026.5.1, 2026.6.0
Fixed versions
2026.1.5, 2026.4.2, 2026.5.1

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that discourse and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
CWE
CWE-79