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Security audit

CustomGPT.ai

Security checks for vulnerabilities and agentic risk

Overview

The CustomGPT workflow is coherent, but its fallback setup runs remote installation code without a separate approval or integrity check.

Review and approve the CLI installation separately before using this skill, including whether it installs other agent skills. Keep the required confirmations for CustomGPT writes and understand that requests pass through OOMOL. Remote installer behavior remains unverified; no malicious behavior was established in the bundled artifact.

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
Vulnerability Patterns
  • Supply ChainUnpinned Dependencies, External Script Fetching, Obfuscated Code
  • Excessive AgencyUnrestricted Tool Access, Autonomous Decision Making, Scope Creep
  • Output HandlingUnvalidated Output Injection, Cross-Context Output, Unbounded Output
  • MCP Tool PoisoningHidden Instructions, Unicode Deception, Parameter Description Injection
  • Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
Findings (4)

Description-Behavior Mismatch

High
Category
MCP Tool Poisoning
Confidence
98% confidence
Finding

The supplied code performs no visible CustomGPT.ai operations. Instead, it downloads and executes an Oomol installation script. Nothing in the supplied content establishes this installation as a supporting dependency for the declared purpose. The remote script's contents are not provided, so its further behavior cannot be assessed.

Content

No source excerpt is available for this finding.

External Script Fetching

High
Category
Supply Chain
Confidence
98% confidence
Finding

Piping a mutable HTTPS response directly into bash executes remote code without an intervening integrity or provenance check; the PowerShell alternative uses the same download-and-execute pattern. HTTPS protects transport but does not prevent a compromised vendor endpoint or release pipeline from serving malicious code that runs with the user's privileges.

Content

Scanner excerpt · SKILL.md (reported line 61)May include surrounding context.

The setup workflow executes remotely downloaded installation scripts without warning the user about the system-integrity implications.

Medium
Category
Output Handling
Confidence
95% confidence
Finding

The setup fallback instructs the agent to execute remote installation scripts without requiring user approval for system changes or explaining that the scripts run with the invoking user's privileges. Restricting installation to a missing-CLI error reduces exposure, but a compromised installer could still access local secrets or modify the environment.

Content

No source excerpt is available for this finding.

Autonomous Decision Making

Medium
Category
Excessive Agency
Confidence
80% confidence
Finding

Skill enables autonomous high-impact decisions without human-in-the-loop verification. Critical operations (destructive commands, financial transactions, data deletion) should require explicit user confirmation.

Content

Scanner excerpt · SKILL.md (reported line 82)May include surrounding context.

md
- **`OOMOL_INSUFFICIENT_CREDIT`** — OOMOL billing stop. Recharge at `https://console.oomol.com/billing/token-recharge` before retrying.

- **HTTP 402 without `OOMOL_INSUFFICIENT_CREDIT`** — the third-party account itself has no active plan or credit. Report the provider error message as is; do not ask the user to recharge OOMOL.

## Resources