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Security audit

The skill for chess player

Security checks for vulnerabilities and agentic risk

Overview

This skill only looks up public Chess.com ratings for a user-provided username and does not show hidden, persistent, destructive, or credential-seeking behavior.

Before installing, understand that this skill contacts Chess.com's public API with the username you provide and returns output mostly in French. Do not provide passwords, tokens, or private account data; the reviewed artifact does not need them.

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 (4)

Lp3

Medium
Category
MCP Least Privilege
Confidence
70% confidence
Finding
Without declared permissions the skill's intent is opaque and cannot be validated.

External Transmission

Medium
Category
Data Exfiltration
Content
import urllib.error
from datetime import datetime, timezone

API_URL = "https://api.chess.com/pub/player/{username}/stats"

def to_date(ts: int | None) -> str:
    if not ts:
Confidence
60% confidence
Finding
Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.

Natural-Language Policy Violations

Low
Confidence
97% confidence
Finding
This code emits user-facing status, usage, and error messages in French, such as "Rating actuel" and "Erreur: username invalide", with no option to choose another language. That is a natural-language locale policy issue because the skill imposes a specific language without opt-in or justification.

Natural-Language Policy Violations

Low
Confidence
91% confidence
Finding
The manifest description and operational instructions are entirely in French, including required output guidance and workflow steps. This can violate a language/locale policy when the skill forces one language without offering the user a choice or documenting a justified locale restriction.

Static analysis

No suspicious patterns detected.