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Security audit

Beszel Check

Security checks for vulnerabilities and agentic risk

Overview

This Beszel monitoring skill is mostly purpose-aligned, but it handles login credentials in an unsafe and under-disclosed way.

Review before installing. Use this only with a trusted local Beszel instance unless the code is changed to use HTTPS correctly, and avoid putting reusable passwords into an environment that may be logged or inherited broadly. The documented commands should be changed to run the script directly instead of sourcing ~/.zshrc.

Vulnerability Patterns
  • Insecure Skill Coding PracticesFinds exploitable flaws such as hardcoded secrets or command injection
  • 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
Findings (2)

T09 · Insecure Skill Coding Practices

Error
Location
index.js:2
Finding

Beszel Credentials and Authorization Tokens Transmitted over Plaintext HTTP

Content
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{ const options = { hostname: new URL(CONFIG.host).hostname, port: new URL(CONFIG.host).port, path: path, method: method, headers: { 'Content-Type': 'application/json', } }; if (token) { options.headers['Authorization'] = token; } const req = https.request(options, (res) => { ``` ```js // 1. Authenticate const auth = await request('/api/collections/users/auth-with-password', 'POST', { identity: CONFIG.email, password: CONFIG.password }); if (!auth.token) { console.error('Authentication failed:', auth); process.exit(1); } const token = auth.token; ``` ### Technical Analysis The variable named `https` imports Node.js's plaintext `http` module rather than the `https` module. All requests therefore use unencrypted HTTP, including the authentication request containing `BESZEL_USER` and `BESZEL_PASS` and subsequent requests containing the authorization token. The implementation extracts only the hostname and port from `BESZEL_HOST`; it does not use the configured URL protocol to select a transport. Consequently, setting `BESZEL_HOST` to an `https://` URL does not enable TLS. The code will still attempt a plaintext HTTP connection to the selected host and port. Sending authentication material to the configured Beszel endpoint is necessary for the declared monitoring functionality. However, sending reusable credentials and tokens without transport encryption is not necessary and ...[truncated 1551 chars]
Remediation
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T09 · Insecure Skill Coding Practices

Note
Location
SKILL.md:14
Finding

Documented Launcher Executes the User's Entire Shell Initialization File

Content
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Remediation
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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
87% confidence
Finding

The skill invokes shell commands that source the user's shell configuration and run a local Node script, which implies access to environment-derived capabilities, but it declares no tool scope such as permissions or allowed-tools. This creates an authorization and transparency gap: the agent may inherit sensitive environment variables or broader execution capability than users expect, increasing the risk of secret exposure or unintended command execution.

Content

No source excerpt is available for this finding.

Missing User Warnings

Medium
Category
Not specified by scanner
Confidence
89% confidence
Finding

This code reads credentials from environment variables and transmits them in a login request, but there is no confirmation prompt, user-facing notice, or explanatory comment/docstring warning that the skill will authenticate to a remote service using supplied credentials. The existing error message at L012 only states that the variables must be set; it does not disclose the network transmission or credential use.

Content

No source excerpt is available for this finding.

Static analysis

No suspicious patterns detected.