{
 "public_id": "AIR-2026-0201",
 "incident_id": "2026-08-microsoft-copilot-cowork-sandbox-bypass",
 "date_disclosed": "2026-08-19",
 "date_occurred": null,
 "title": "Microsoft Copilot Cowork sandbox bypass: malicious Skills reach attacker servers through the out-of-sandbox file sync service for C2 and exfiltration",
 "class": "responsible_disclosure",
 "attack_surface": "enterprise_assistant",
 "initial_vector": "malicious_skill",
 "agent_capability_abused": [
  "skill_execution",
  "file_sync_service",
  "background_process_persistence"
 ],
 "target_product": "Microsoft Copilot Cowork",
 "target_vendor": "Microsoft",
 "autonomy_level": "semi_autonomous",
 "impact_realized": false,
 "impact_type": [
  "data_exfiltration",
  "remote_control"
 ],
 "blast_radius": "M365 tenants using Copilot Cowork with user- or org-shared Skills",
 "cve": [],
 "taxonomy": {
  "owasp_asi": [
   "ASI01",
   "ASI05",
   "ASI04"
  ],
  "mitre_atlas": [],
  "labels": [
   "sandbox_escape",
   "command_and_control",
   "skill_poisoning",
   "stop_button_ineffective"
  ]
 },
 "defense_present": "Copilot Cowork code sandbox with network restrictions",
 "defense_bypassed": true,
 "fix_shipped": "mitigated 2026-08-19",
 "primary_sources": [
  "https://www.promptarmor.com/resources/microsoft-copilot-cowork-sandbox-bypass"
 ],
 "verified_quote": "A sandbox bypass in Microsoft Copilot Cowork allowed malicious Skills to communicate with attacker servers to retrieve commands and exfiltrate any data the agent could access.",
 "confidence": "high",
 "notes": "PromptArmor. Reported 2026-06-24, mitigated 2026-08-19. The file sync service sits outside the sandbox and accepts arbitrary URLs, giving a two-way channel. Notable secondary finding: 'Processes running in the background in the sandbox continue to execute even when an agent's turn ends' - clicking stop does not halt the attack. Data reachable included Outlook, SharePoint, Teams, plugins and chat history.",
 "risk_category": "security_fraud",
 "risk_secondary": [
  "privacy"
 ],
 "risk_subcategory": "Supply Chain Compromise",
 "risk_sub_secondary": [
  "Remote Code Execution & Sandbox Escape",
  "Persistence & Covert C2"
 ],
 "ai_entity": "generative",
 "agency": "agent_acted",
 "agency_debatable": false,
 "agency_reason": "the Skill reached attacker servers through the file sync service",
 "vector_family": "malicious_component",
 "vector_detail": "malicious_skill",
 "guardrail_kind": [
  "sandbox_isolation",
  "permission_scope"
 ],
 "guardrail_outcome": "silent",
 "xrefs": {
  "aiid": [],
  "atlas": [],
  "cve": [],
  "ghsa": []
 },
 "primary_asi": "ASI01",
 "agent_framework": "unknown",
 "model_provider": "microsoft",
 "model_name": "",
 "detection_mechanism": "external_researcher",
 "tool_access": "unknown",
 "financial_loss_band": "unknown",
 "eai_category": "supply_chain_vulnerabilities",
 "eai_domain": "tool_misuse",
 "eai_secondary": [
  "privilege_escalation",
  "data_exfiltration_channels"
 ],
 "eai_reason": "subcategory: Supply Chain Compromise",
 "asi_curated": [
  "ASI01",
  "ASI05"
 ],
 "asi_scope": "in_scope",
 "asi_provenance": "curated_plus_rule",
 "asi_reason": "curated: ASI01,ASI05 | added ASI04 (vector_family=malicious_component)",
 "submitted_by": "EAI Internal"
}