Disposable Email For Agents

• Outcome: Review
• Latest audit: Sep 10, 2026 · 11:19 PM UTC
• Version: 1.0.0

Overview

This skill does what it says, but it routes email and attachments through a remote service and uses an unpinned runtime MCP dependency that deserves review before installation.

Review this skill before installing. Use it only for low-sensitivity disposable inbox workflows, avoid password resets or regulated personal data, treat all email content and attachments as untrusted, and prefer a pinned, verified mcp-remote installation in a constrained environment.

A.I.G

Vulnerability Patterns

• Insecure Dependencies: Introduces malicious components through unsafe dependency sources
• Skill Instruction Hijacking: Alters the agent's session goals or safety constraints when the skill loads
• Agent Memory Poisoning: Writes attacker-controlled rules into memory that affect later sessions
• Remote Payload Retrieval and Execution: Fetches external code whose behavior can change after review
• Embedded Malicious Code: Ships malicious scripts inside the skill and executes them locally

Findings (1)

T08 · Insecure Dependencies

Error

• Location: SKILL.md:8

Finding

Unpinned MCP Package Execution Through npx

Content

View full analysis

Vulnerability Details

File Location: SKILL.md, lines 8-14
Vulnerability Type: Unpinned third-party executable dependency
Risk Level: High

Vulnerable Code

json

{
  "mcpServers": {
    "myagentinbox": {
      "command": "npx",
      "args": ["mcp-remote", "https://myagentinbox.com/mcp"]
    }
  }
}

Technical Analysis

The MCP configuration invokes mcp-remote through npx without specifying an exact package version or verifying package integrity. If the package is not already available in the execution environment, npx may resolve and download executable package code from the npm registry at setup or runtime.

Because no version, lockfile, checksum, or controlled installation source is specified, the code executed by this configuration can differ from the version that was originally reviewed. A compromised maintainer account, malicious package release, registry compromise, or unexpected upstream update could therefore introduce arbitrary executable behavior.

The configuration also connects the package to the externally operated MCP endpoint https://myagentinbox.com/mcp. The endpoint's tools and responses can change independently of this static Skill. This increases the trust placed in external infrastructure, although the confirmed dependency vulnerability is specifically the unpinned local execution of mcp-remote.

Attack Path

1. An attacker compromises the mcp-remote package, its publishing account, or its distribution channel and publishes a malicious version.
2. A user installs or activates the Skill in an environment where the package is not pinned and securely preinstalled.
3. The configured npx mcp-remote command resolves the attacker-controlled or compromised package version.
4. npx downloads and executes the package under the identity and permissions of the Agent process.
5. Malicious package code accesses resources available to that process, performs un ...[truncated 575 chars]

Remediation

View remediation

Remediation Suggestions

1. Pin mcp-remote to a specific, audited version rather than relying on unversioned npm resolution.
2. Install the dependency during a controlled build or deployment stage using a committed lockfile and integrity metadata.
3. Avoid runtime package installation through npx; invoke a verified local executable from an immutable installation instead.
4. Verify the package publisher, source repository, release provenance, and dependency tree before deployment.
5. Use npm integrity checks, a trusted internal registry or allowlist, and automated dependency scanning.
6. Run the MCP client with least privilege in an isolated environment that restricts filesystem access, environment variables, subprocess creation, and outbound network destinations.
7. Restrict outbound connectivity to the expected MCP host and validate its TLS identity.
8. Treat remote MCP responses, email bodies, and downloaded attachments as untrusted data; do not execute attachments or interpret message content as Agent instructions without explicit validation.

SkillSpector

Vulnerability Patterns

• Data Exfiltration: External Transmission, Env Variable Harvesting, File System Enumeration
• Prompt Injection: Instruction Override, Hidden Instructions, Exfiltration Commands
• Privilege Escalation: Excessive Permissions, Sudo/Root Execution, Credential Access
• Supply Chain: Unpinned Dependencies, External Script Fetching, Obfuscated Code
• Excessive Agency: Unrestricted Tool Access, Autonomous Decision Making, Scope Creep

Findings (1)

Missing User Warnings

Medium

• Category: Not specified by scanner
• Confidence: 92% confidence

Finding

This skill enables an agent to send email content and attachments through a third-party remote MCP service, but it does not warn users that sensitive message bodies, sender metadata, and downloaded files may be exposed to that external provider. In an agent context, inboxes may receive password resets, verification links, personal data, or malicious attachments, so the absence of a clear privacy and safety warning can lead to unintended disclosure and unsafe handling of untrusted content.

Content

No source excerpt is available for this finding.