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Security audit

Crypto Tax Agent

Security checks for vulnerabilities and agentic risk

Overview

This is a coherent crypto tax reporting skill, but users should handle wallet and tax data carefully before using third-party blockchain APIs.

Before installing, confirm that any client or personal wallet addresses may be queried through third-party services, avoid sharing API keys or private keys with the agent, and have a CPA or tax attorney review uncertain positions such as bridge events, LP activity, privacy coins, sanctions exposure, and current-year law changes.

A.I.G

Vulnerability Patterns
  • Skill Instruction HijackingAlters the agent's session goals or safety constraints when the skill loads
  • Agent Memory PoisoningWrites attacker-controlled rules into memory that affect later sessions
  • Remote Payload Retrieval and ExecutionFetches external code whose behavior can change after review
  • Embedded Malicious CodeShips malicious scripts inside the skill and executes them locally
  • Unauthorized Access and Privilege EscalationObtains permissions beyond the task's legitimate needs

SkillSpector

Vulnerability Patterns
  • Data ExfiltrationExternal Transmission, Env Variable Harvesting, File System Enumeration
  • MCP Tool PoisoningHidden Instructions, Unicode Deception, Parameter Description Injection
  • Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
  • Privilege EscalationExcessive Permissions, Sudo/Root Execution, Credential Access
  • Supply ChainUnpinned Dependencies, External Script Fetching, Obfuscated Code
Findings (4)

Intent-Code Divergence

Medium
Confidence
92% confidence
Finding
Line L034 states the skill reports and does not provide planning or structural advice. However, lines L169-L173 prescribe a default substantive tax position for cross-chain bridges ('default to the non-taxable transfer treatment'), which is a recommendation about tax treatment rather than neutral reporting.

Missing User Warnings

Medium
Confidence
96% confidence
Finding
The skill directs transmission of wallet addresses and detailed transaction histories to third-party services such as Etherscan, Helius, and CoinGecko without an explicit consent, minimization, or privacy-warning step. Even if wallet data is public on-chain, associating addresses with a client tax engagement can reveal sensitive financial profiles and create confidentiality, vendor-risk, and regulatory exposure.

External Transmission

Medium
Category
Data Exfiltration
Content
### Etherscan V2 Unified API

**Base endpoint**: `https://api.etherscan.io/v2/api`

A single API key covers all major EVM chains:
Confidence
90% confidence
Finding
This is a real external-transmission surface because the skill explicitly instructs sending wallet addresses and transaction-query parameters to an external API endpoint. In the tax context, this is more sensitive than ordinary blockchain lookups because the queried addresses are tied to an identified client and may expose a comprehensive financial history to a third party.

Description-Behavior Mismatch

Low
Confidence
77% confidence
Finding
The manifest describes a crypto tax compliance skill focused on transaction analysis, reconciliation, and tax form preparation. In the 'WHEN NOT TO USE' section, the documentation directs the agent to 'stop work, notify client, escalate to counsel,' which goes beyond analytical/reporting behavior into case-handling workflow actions not reflected in the manifest description.

Static analysis

No suspicious patterns detected.