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Security audit

x402-api-quickstart

Security checks for vulnerabilities and agentic risk

Overview

This skill is a small, transparent x402 payment quickstart, but it gives agents broad instructions for making paid API calls without clear spending limits or confirmation rules.

Review before installing if your agent has access to a funded Base wallet or can authorize payments. Use only known x402 endpoints, set a per-call and session spending cap, and require explicit approval before paying a new host or an amount outside the listed examples.

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
  • Trigger AbuseOverly Broad Trigger, Shadow Command Trigger, Keyword Baiting Trigger
  • Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
  • Privilege EscalationExcessive Permissions, Sudo/Root Execution, Credential Access
  • Supply ChainUnpinned Dependencies, External Script Fetching, Obfuscated Code
Findings (2)

Vague Triggers

Medium
Category
Not specified by scanner
Confidence
89% confidence
Finding

The skill explicitly teaches agents to call "ANY x402 pay-per-call HTTP API," which creates an overly broad operational scope for autonomous use. In security terms, this can enable an agent to send requests and potentially authorize micropayments to arbitrary third-party endpoints without adequate allowlisting, user approval, or domain-specific constraints.

Content

No source excerpt is available for this finding.

External Transmission

Medium
Category
Data Exfiltration
Confidence
50% confidence
Finding

Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Content

Scanner excerpt · SKILL.md (reported line 20)May include surrounding context.

The 4-step flow (works for any x402 API)

text
1. GET https://api.example.com/endpoint
   -> HTTP 402 + X-PAYMENT-REQUIREMENTS header (JSON: scheme, asset, amount)
2. Parse requirements: scheme=exact, asset=USDC 0x8335...2913 (Base),
   payTo=<seller address>, amount=<atomic units>

Static analysis

No suspicious patterns detected.