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Security audit

TaxJar

Security checks for vulnerabilities and agentic risk

Overview

TaxJar changes require user approval, but missing software triggers a remote installer without a separate approval step or integrity check.

Review the CLI installation separately before allowing setup, preferably using a pinned and verified release. Consider its effects on other installed agent skills and OOMOL's handling of your TaxJar data. Keep the explicit approvals for account changes and deletions. The artifacts support installation-control concerns, but do not establish malicious behavior.

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 command runs an external installer rather than performing TaxJar data operations. Nothing provided establishes this installer as a supporting dependency for TaxJar functionality. The remote script's contents are unavailable, so its specific effects cannot be determined from this code chunk.

Content

No source excerpt is available for this finding.

External Script Fetching

High
Category
Supply Chain
Confidence
98% confidence
Finding

The command immediately executes a remotely downloaded script without a pinned version or integrity verification; the PowerShell alternative has the same weakness. If the distribution endpoint or its publishing infrastructure is compromised, attacker-controlled code could execute with the agent process's local privileges and access files or credentials; HTTPS alone does not establish artifact integrity.

Content

Scanner excerpt · SKILL.md (reported line 75)May include surrounding context.

Fallback setup executes remote installation scripts without warning about system changes or external code execution.

Medium
Category
Output Handling
Confidence
92% confidence
Finding

The fallback directs the agent to install software without requiring user approval or explaining that downloaded code will execute and may modify the local environment. Restricting this to a missing-CLI error reduces exposure, but authorization to perform a TaxJar task does not necessarily authorize installing software.

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 96)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