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Security audit

Yunbiao

Security checks for vulnerabilities and agentic risk

Overview

The Yunbiao workflow includes clear approval safeguards, but its setup fallback runs remote installer code without a separate approval step or integrity check.

Review and approve CLI installation separately, preferably using a pinned, verified release, before allowing the fallback to run. Connect only the Yunbiao account and permissions needed, and retain the required approvals for business-data and account changes. The entire bundled skill was inspected, but the external installer and connector implementation remain unverified; no malicious behavior was established.

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
96% confidence
Finding

The supplied chunk runs an Oomol-hosted installer, while the description declares Yunbiao data management. Nothing in the supplied code establishes that this installation supports Yunbiao, so it cannot be treated as a demonstrated supporting implementation detail. The remote script's contents and downstream effects are not available for assessment.

Content

No source excerpt is available for this finding.

External Script Fetching

High
Category
Supply Chain
Confidence
98% confidence
Finding

Piping a remotely fetched script directly into Bash executes whatever the installation endpoint returns with the invoking user's privileges, without a pinned version or independently verified integrity. A compromised vendor endpoint or distribution pipeline could therefore execute arbitrary local code; HTTPS does not protect against compromise of the publisher. The PowerShell example has the same risk, although installation is only a fallback and the domain belongs to the expected CLI provider.

Content

Scanner excerpt · SKILL.md (reported line 73)May include surrounding context.

Fallback setup executes remotely downloaded installer scripts without warning the user about local code execution and system changes.

Medium
Category
Output Handling
Confidence
94% confidence
Finding

The missing-CLI fallback directs the agent to execute an installer without explicitly obtaining permission for local code execution or explaining its system changes. Permission to perform Yunbiao operations does not necessarily authorize installing software, and the write/destructive confirmation rules only address Yunbiao state. The conditional fallback reduces exposure but does not resolve this consent gap.

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 94)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