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Security audit

SignWell

Security checks for vulnerabilities and agentic risk

Overview

The SignWell workflow is coherent, but automatic software installation and undisclosed changes to other agent skills warrant review.

Review and approve CLI setup separately before allowing the automatic fallback. OOMOL will mediate access to your SignWell account and document data. Prefer a reviewed CLI version, retain confirmation for document changes and sending, and consider the documented OO_SKILLS_SYNC_DISABLED setting to prevent startup skill synchronization. The bundle contains only instructions; installer and backend behavior remain unverified.

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 code performs remote installation rather than any visible SignWell operation. Dependency installation can be a supporting implementation detail, but the supplied material does not establish that this installer supports the declared SignWell functionality. The downloaded script's contents and any further 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

The command pipes a remotely retrieved, unpinned script directly into Bash; the PowerShell alternative similarly executes downloaded content immediately. If the installer distribution infrastructure is compromised, attacker-controlled code could execute with the agent process's local permissions and access available files or credentials; HTTPS alone does not establish artifact integrity.

Content

Scanner excerpt · SKILL.md (reported line 60)May include surrounding context.

Setup executes remote installation scripts without warning about local system changes.

Medium
Category
Output Handling
Confidence
94% confidence
Finding

The missing-CLI fallback instructs the agent to install software without explaining local system changes or requesting approval. Although installation is conditional and relevant to the task, permission to operate SignWell does not necessarily authorize executing an installer or modifying the local 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 81)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