Research demo
WhatsApp MCP exploited: a sleeper MCP server rewrites its tool descriptions after install to exfiltrate the user's entire WhatsApp history
AIR-2025-0018 AIR record · 2025-04-invariant-whatsapp-mcp-exfiltration
From the supporting source
An untrusted MCP server can attack and exfiltrate data from an agentic system that is also connected to a trusted WhatsApp MCP instance, side-stepping WhatsApp's encryption and security measures.invariantlabs.ai
The record
Disclosed
2025-04-07
Vendor
open source / MCP ecosystem
Product
whatsapp-mcp (lharries) connected alongside an untrusted MCP server
Risk domain
Privacy › Data exfiltration channels
Also touches
Supply chain vulnerabilities
System type
Generative model
Who acted
Agent acted — the agent read the whole WhatsApp history and sent it out
Attack surface
MCP server
Autonomy level
Semi-autonomous
Initial vector
Malicious mcp server tool description rug pull
Impact type
Data exfiltration
Confidence
High
Submitted by
EAI Internal
Crosswalk
- OWASP Agentic Top 10 (2026)
- ASI02 – Tool Misuse and Exploitation
- MITRE ATLAS
- AML.T0024 – Exfiltration via AI Inference API
- NIST AI RMF
- MAP 4.2
- EU AI Act
- Article 10
- ISO/IEC
- TR 24028; 23894
- AIUC-1
- A. Data & Privacy
- Scope
- tool misuse
- Mitigation
- Monitor network traffic for anomalous patterns; Restrict egress destinations.
- Taxonomy
- Enkrypt AI agent risk taxonomy · Black-Box Red Teaming of Agentic AI: A Taxonomy-Driven Framework for Automated Risk Discovery
Blast radius
any agent host connecting a trusted WhatsApp MCP server alongside an untrusted one
Capability abused
Defense & remediation
Recorded defense
none - agent hosts did not validate tool description changes
Guardrail kinds
None
Guardrail outcome
Not applicable
Fix shipped
none; recommendation is caution with untrusted MCP servers and use of MCP-Scan
Taxonomy & references
Curator notes
Invariant Labs (acquired by Snyk 2025-06-24). Companion to their tool-poisoning notification (2025-04-invariant-mcp-tool-poisoning) but a distinct incident: this is the cross-server shadowing case where a benign-at-install 'sleeper' server later swaps in malicious tool descriptions. The end-to-end-encryption sidestep is the headline - the attack happens at the agent, after decryption. Updated 2025-04-09.
Supporting sources
Cite as
Enkrypt AI. "WhatsApp MCP exploited: a sleeper MCP server rewrites its tool descriptions after install to exfiltrate the user's entire WhatsApp history". AIR, AIR-2025-0018. https://agentincident.vercel.app/i/AIR-2025-0018/ (accessed 2026-10-19).