Hackage package metadata stored XSS vulnerability

{
  "affected": [
    {
      "database_specific": {
        "human_link": "https://github.com/haskell/security-advisories/tree/main/advisories/published/2026/HSEC-2026-0004.md",
        "osv": "https://raw.githubusercontent.com/haskell/security-advisories/refs/heads/generated/osv-export/2026/HSEC-2026-0004.json"
      },
      "package": {
        "ecosystem": "Hackage",
        "name": "hackage-server"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "severity": [
        {
          "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L",
          "type": "CVSS_V3"
        }
      ]
    }
  ],
  "database_specific": {
    "home": "https://github.com/haskell/security-advisories",
    "osvs": "https://raw.githubusercontent.com/haskell/security-advisories/refs/heads/generated/osv-export",
    "repository": "https://github.com/haskell/security-advisories"
  },
  "details": "# Hackage package metadata stored XSS vulnerability\n\nUser-controlled metadata from `.cabal` files are rendered into HTML\n`href` attributes without proper sanitization, enabling stored\nCross-Site Scripting (XSS) attacks.  The specific fields affected\nare:\n\n- `homepage`\n- `bug-reports`\n- `source-repository.location`\n- `description` (Haddock hyperlinks)\n\nThe Haskell Security Response Team audited the entire corpus of\n**published** packages on `hackage.haskell.org`\u2014all published\npackage versions but *not* candidates.  No exploitation attempts\nwere detected.\n\nTo fix the issue, *hackage-server* now inspects target URIs and only\nproduces a hyperlink when the URI has an approved scheme: `http`,\n`https`, and (only for some fields) `mailto`.\n\nThe fix has been [committed][commit] and deployed on\n`hackage.haskell.org`.  Other operations of *hackage-server*\ninstances should update as soon as possible to commit\n`2de3ae45082f8f3f29a41f6aff620d09d0e74058` or later.\n\n## Acknowledgements\n\n- **Joshua Rogers** (https://joshua.hu/) of AISLE\n  (https://aisle.com/) reported the issue to the Haskell Security\n  Response Team.\n- **Fraser Tweedale** implemented the fix.\n- **Gershom Bazerman** merged the fix and deployed it to\n  `hackage.haskell.org`.\n\n[commit]: https://github.com/haskell/hackage-server/commit/2de3ae45082f8f3f29a41f6aff620d09d0e74058\n",
  "id": "HSEC-2026-0004",
  "modified": "2026-03-28T16:05:12Z",
  "published": "2026-03-28T16:05:12Z",
  "references": [
    {
      "type": "FIX",
      "url": "https://github.com/haskell/hackage-server/commit/2de3ae45082f8f3f29a41f6aff620d09d0e74058"
    }
  ],
  "schema_version": "1.5.0",
  "summary": "Hackage package metadata stored XSS vulnerability"
}