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GHSA-CX86-7XWP-W9WF

Vulnerability from github – Published: 2026-09-18 16:58 – Updated: 2026-09-18 16:58
VLAI
Summary
Semantic MediaWiki affected by reflected XSS in `Special:Ask` via a forged cursor pagination token
Details

Reflected XSS via a forged cursor pagination token

Failure mode

Special:Ask accepts a cursor query parameter for keyset pagination (added in 7.0.0). The token is decoded by CursorEncoder, which is an unsigned base64url-encoded JSON blob, so its contents are fully attacker-controlled. When the cursor's sort anchor does not match the request's sort= / order=, QueryCreator::applyCursorIfRequested() builds an error message by interpolating the attacker-controlled sort_prop / sort_order values into a raw string via Query::addErrors().

Unlike SMW's message-key errors, this raw string bypasses the message layer's sanitisation (ProcessingErrorMsgHandler::normalizeAndDecodeMessages() passes a non-key, non-encoded string through unchanged). ErrorWidget::queryError() then assembles the errors and passes them to Html::errorBox(), whose first argument is emitted as raw HTML. The result is a reflected cross-site scripting vulnerability: a crafted cursor token containing markup in sort_prop (or sort_order) executes script in the victim's browser on the wiki origin.

No authentication or special permission is required. The payload is delivered via a crafted link, e.g. Special:Ask?q=...&p[cursor]=<forged token> where the token decodes to {"v":1,"sort_prop":"<script>...</script>"}. Confirmed executing in a browser; the responses carry no Content-Security-Policy, so inline script is not blocked.

Remediation

  • Output-encode the attacker-controlled sort_prop / sort_order values before they are interpolated into the error text in QueryCreator, so no raw user input enters the error stream.
  • Defense in depth: the format=debug output path that reflected the same error text was hardened separately in GHSA-q5fm-9mx6-44f4.

Maintenance note

Query error strings are rendered as raw HTML by ErrorWidget::queryError() via Html::errorBox(). Any error added through Query::addErrors() that embeds user-controlled text must be output-encoded (or use a message key); pagination and validation error text is attacker-influenced and must not be treated as trusted.

Show details on source website

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 7.1.0"
      },
      "package": {
        "ecosystem": "Packagist",
        "name": "mediawiki/semantic-media-wiki"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "7.0.0"
            },
            {
              "fixed": "7.2.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-77616"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-18T16:58:50Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Reflected XSS via a forged cursor pagination token\n\n#### Failure mode\n\n`Special:Ask` accepts a `cursor` query parameter for keyset pagination (added in 7.0.0). The token is decoded by `CursorEncoder`, which is an **unsigned** base64url-encoded JSON blob, so its contents are fully attacker-controlled. When the cursor\u0027s sort anchor does not match the request\u0027s `sort=` / `order=`, `QueryCreator::applyCursorIfRequested()` builds an error message by interpolating the attacker-controlled `sort_prop` / `sort_order` values into a raw string via `Query::addErrors()`.\n\nUnlike SMW\u0027s message-key errors, this raw string bypasses the message layer\u0027s sanitisation (`ProcessingErrorMsgHandler::normalizeAndDecodeMessages()` passes a non-key, non-encoded string through unchanged). `ErrorWidget::queryError()` then assembles the errors and passes them to `Html::errorBox()`, whose first argument is emitted as raw HTML. The result is a reflected cross-site scripting vulnerability: a crafted `cursor` token containing markup in `sort_prop` (or `sort_order`) executes script in the victim\u0027s browser on the wiki origin.\n\nNo authentication or special permission is required. The payload is delivered via a crafted link, e.g. `Special:Ask?q=...\u0026p[cursor]=\u003cforged token\u003e` where the token decodes to `{\"v\":1,\"sort_prop\":\"\u003cscript\u003e...\u003c/script\u003e\"}`. Confirmed executing in a browser; the responses carry no Content-Security-Policy, so inline script is not blocked.\n\n#### Remediation\n\n- Output-encode the attacker-controlled `sort_prop` / `sort_order` values before they are interpolated into the error text in `QueryCreator`, so no raw user input enters the error stream.\n- Defense in depth: the `format=debug` output path that reflected the same error text was hardened separately in GHSA-q5fm-9mx6-44f4.\n\n#### Maintenance note\n\nQuery error strings are rendered as raw HTML by `ErrorWidget::queryError()` via `Html::errorBox()`. Any error added through `Query::addErrors()` that embeds user-controlled text must be output-encoded (or use a message key); pagination and validation error text is attacker-influenced and must not be treated as trusted.",
  "id": "GHSA-cx86-7xwp-w9wf",
  "modified": "2026-09-18T16:58:50Z",
  "published": "2026-09-18T16:58:50Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/SemanticMediaWiki/SemanticMediaWiki/security/advisories/GHSA-cx86-7xwp-w9wf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/SemanticMediaWiki/SemanticMediaWiki"
    },
    {
      "type": "WEB",
      "url": "https://github.com/SemanticMediaWiki/SemanticMediaWiki/releases/tag/7.2.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Semantic MediaWiki affected by reflected XSS in `Special:Ask` via a forged cursor pagination token"
}



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