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Security audit

Vynn Backtester

Security checks for vulnerabilities and agentic risk

Overview

This skill is a disclosed Vynn API integration for running trading backtests, with expected use of an API key and outbound requests.

Before installing, use a dedicated Vynn API key and avoid submitting confidential trading logic or sensitive portfolio information unless you trust the Vynn service and its retention claims. If you set VYNN_BASE_URL, ensure it points to a trusted endpoint because the API key will be sent there.

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 Least PrivilegeUnderdeclared Capability, Wildcard Permission, Missing Permission Declaration
  • 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)

Undeclared Tool Scope

Medium
Category
MCP Least Privilege
Confidence
92% confidence
Finding

The skill documents and requires sensitive capabilities (env access for VYNN_API_KEY and outbound network access) but does not declare any explicit tool scope such as permissions or allowed-tools. That creates a transparency and least-privilege problem: an agent or reviewer cannot easily verify what the skill is expected to access, increasing the chance of over-broad execution or accidental misuse.

Content

No source excerpt is available for this finding.

External Transmission

Medium
Category
Data Exfiltration
Confidence
60% 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 39)May include surrounding context.

bash
# Sign up (instant, returns your API key)
curl -X POST https://the-vynn.com/v1/signup -H "Content-Type: application/json" -d '{"email": "you@example.com"}'

# Set the key
export VYNN_API_KEY="vynn_free_..."

Static analysis

No suspicious patterns detected.