TC-2025-0042 · GH · LURE

rules-file-backdoor/[email protected]

Rules File Backdoor: hides invisible Unicode tag/bidirectional characters inside .cursorrules and .github/copilot-instructions.md to force coding agents to inject backdoors into generated application code.

Primary advisory (Pillar Security) Back to all 66 records

Signed ledger verdict

TC-2025-0042

Known bad (exit 2) gh:rules-file-backdoor/cursorrules-unicode-poison

IOC & scope: gh:rules-file-backdoor/cursorrules-unicode-poison (.cursorrules / .github/copilot-instructions.md). Verified by human review and signed into the CC-BY 4.0 OSV v1.6.0 feed.

Credited finder: Pillar Security ↗
Recorded timestamp: 2025-03-19
Canonical SHA-256: 5560a06bffab05e7…
Local hook action: Block (exit 2)

Run live in Counter Workbench

Signed in /feed.json (.sig).

01 8-Vector Capability X-Ray (ABOM) & OWASP Agentic Crosswalk

Deterministic capability profile and taxonomy mapping.

Every artifact in the threat.cafe ledger is profiled across eight execution vectors and mapped to the OWASP Top 10 for Agentic Applications (ASI01-ASI10) and Agentic Skills & Tools (AST01-AST10).

8-Vector Capability X-Ray (ABOM)

1. Filesystem
Sensitive paths touched: .cursorrules, .github/copilot-instructions.md, CLAUDE.md
2. Environment
Variables harvested: None observed
3. Network
Outbound egress domains: None observed
4. Subprocess
Process execution primitives: None observed
5. Lifecycle
Install / startup hooks: None observed
6. OAuth / MCP
Declared scopes: None observed
7. Obfuscation
Encoding / steganography: unicode_bidi_tags_u202e_ue0001
8. Provenance
Attestation status: poisoned_repo_rules_file

Governance & detector mapping

OWASP Agentic ASI (2026): ASI01 (Agent Goal Hijack), ASI05 (Unexpected Code Execution (RCE))
OWASP Agentic AST (2026): AST01 (Malicious MCP Servers), AST04 (Covert Channel Exfiltration)
Deterministic rules matched: RULE_01_GLASSWORM_UNICODE, RULE_02_PROMPT_OVERRIDE

Version scoping & related records

No other versions of this package are currently listed on the board. Unlisted versions evaluate to unknown under local policy.yml.

Local CLI verification

$ threat-cafe-hook check "gh:rules-file-backdoor/cursorrules-unicode-poison"
[threat.cafe] known_bad: gh:rules-file-backdoor/cursorrules-unicode-poison (TC-2025-0042)
  Reason: Rules File Backdoor: hides invisible Unicode tag/bidirectional characters inside .cursorru
  Source: https://www.pillar.security/blog/new-vulnerability-in-github-copilot-and-cursor-how-hackers-can-weaponize-code-agents (credited to Pillar Security)

OSV v1.6.0 machine-readable record

Included in /feed.json under CC-BY 4.0 license and verified by /feed.json.sig.

{
  "schema_version": "1.6.0",
  "id": "TC-2025-0042",
  "modified": "2025-03-19T12:00:00Z",
  "published": "2025-03-19T12:00:00Z",
  "summary": "Rules File Backdoor: hides invisible Unicode tag/bidirectional characters inside .cursorrules and .github/copilot-instructions.md to force coding agents to inject backdoors into generated application code.",
  "affected": [
    {
      "package": {
        "ecosystem": "gh",
        "name": "rules-file-backdoor/cursorrules-unicode-poison"
      },
      "versions": [
        "1.0.0"
      ]
    }
  ],
  "credits": [
    {
      "name": "Pillar Security",
      "type": "FINDER"
    }
  ],
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.pillar.security/blog/new-vulnerability-in-github-copilot-and-cursor-how-hackers-can-weaponize-code-agents"
    },
    {
      "type": "WEB",
      "url": "https://threat.cafe/incidents/tc-2025-0042/"
    }
  ],
  "database_specific": {
    "target": "gh:rules-file-backdoor/cursorrules-unicode-poison",
    "kind": "lure",
    "verdict": "known_bad",
    "ioc": "gh:rules-file-backdoor/cursorrules-unicode-poison (.cursorrules / .github/copilot-instructions.md)",
    "artifact_sha256": "5560a06bffab05e7b22706c8613aa80e2e7339cf7804dcab878681d12c79ee9d",
    "owasp_asi": [
      "ASI01",
      "ASI05"
    ],
    "owasp_ast": [
      "AST01",
      "AST04"
    ],
    "rules_matched": [
      "RULE_01_GLASSWORM_UNICODE",
      "RULE_02_PROMPT_OVERRIDE"
    ],
    "abom": {
      "fs_sensitive": [
        ".cursorrules",
        ".github/copilot-instructions.md",
        "CLAUDE.md"
      ],
      "env_harvest": [],
      "net_egress": [],
      "proc_exec": [],
      "install_hooks": [],
      "oauth_scopes": [],
      "obfuscation": [
        "unicode_bidi_tags_u202e_ue0001"
      ],
      "provenance": "poisoned_repo_rules_file"
    },
    "license": "CC-BY-4.0",
    "record_digest": "sha256:6f44e9ba87f0a4225ad0b86f60e7137e4440de8248a372a7043570f30f2fb5e8",
    "release_signature_url": "https://threat.cafe/feed.json.sig"
  }
}

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