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Discourse: Reject literal backslash path separators in iframe src traversal guard

Type: advisorySource: Official CVE List1 source record

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.

Announced Source revision 1
Original source ↗

CVE-2026-91123

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: cve:CVE-2026-91123

discourse

Source reference: /containers/cna/affected/0/product

Affected versions
Not stated in this record
Fixed versions
Not stated in this record
Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "vendor": "discourse",
    "product": "discourse",
    "versions": [
      {
        "status": "affected",
        "version": "< 2026.8.0"
      },
      {
        "status": "affected",
        "version": ">= 2026.7.0-latest, < 2026.7.2"
      },
      {
        "status": "affected",
        "version": ">= 2026.6.0-latest, < 2026.6.3"
      },
      {
        "status": "affected",
        "version": ">= 2026.1.0-latest, < 2026.1.8"
      }
    ]
  }
]
Related CVEs
CVE-2026-91123

Source reference: /cveMetadata/cveId

Publisher severity

high

Source reference: /containers/cna/metrics

Event
#1807 · Revision 1
Added to Heist Feed
Publisher date
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