T09 · Insecure Skill Coding Practices
Error
- Location
SKILL.md:31- Finding
Bearer Credential Exposure Through URL Query Parameters and API Responses
- Content
View full analysis
- Remediation
View remediation
Security audit
AgentFuel API
Security checks for vulnerabilities and agentic risk
Overview
The skill is a coherent AgentFuel API guide, but it normalizes putting a paid-service API key in URLs and includes crypto-funded credit actions without enough guardrails.
Review this carefully before installing. Use header-based authorization only, avoid putting real AgentFuel keys in URLs or prompts, rotate any key already used in a query-string URL, and manually confirm invoice amounts, token network, recipient key, and transfer amount before any payment or credit transfer.
Vulnerability Patterns
- Insecure Skill Coding PracticesFinds exploitable flaws such as hardcoded secrets or command injection
- 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
Findings (1)
Vulnerability Patterns
- Data ExfiltrationExternal Transmission, Env Variable Harvesting, File System Enumeration
- Trigger AbuseOverly Broad Trigger, Shadow Command Trigger, Keyword Baiting Trigger
- Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
- Privilege EscalationExcessive Permissions, Sudo/Root Execution, Credential Access
- Supply ChainUnpinned Dependencies, External Script Fetching, Obfuscated Code
Findings (5)
Missing User Warnings
Medium
- Category
- Not specified by scanner
- Confidence
- 98% confidence
- Finding
The skill explicitly recommends passing the AgentFuel API key in the URL query string for web_fetch usage. Query-string secrets are commonly exposed through browser history, server/access logs, analytics, referrers, proxy logs, and agent/tool traces, so this materially increases the chance of credential disclosure.
- Content
Ssd 3
Medium
- Category
- Not specified by scanner
- Confidence
- 99% confidence
- Finding
The documentation encourages placing a real API key in a request URL, which is especially risky in natural-language agent workflows where URLs may be echoed back to the user, stored in transcripts, or captured by observability systems. This can directly leak the credential and enable unauthorized use of the linked paid service balance.
- Content
External Transmission
Medium
- Category
- Data Exfiltration
- Confidence
- 60% confidence
- Finding
Data is being sent to an external URL. This could be legitimate telemetry or data exfiltration. Manual review is recommended.
- Content
With header auth (curl/exec):
bash curl https://agentfuel.dev/v1/balance \ -H "Authorization: Bearer $AGENTFUEL_KEY"
Ssd 3
Medium
- Category
- Not specified by scanner
- Confidence
- 97% confidence
- Finding
The examples normalize use of the real af_ key in query-parameter URLs for invoice-related requests. In agent environments, these full URLs may appear in prompts, tool traces, exception messages, screenshots, or logs, exposing a reusable credential tied to billable resources.
- Content
Missing User Warnings
Medium
- Category
- Not specified by scanner
- Confidence
- 90% confidence
- Finding
The skill documents creating USDT invoices and transferring credits between keys without prominent warnings that these are financial actions and may be irreversible. In an agent context, this can lead users or automated workflows to trigger deposits or transfers without understanding the consequences, increasing the risk of fund loss or unauthorized spend.
- Content
Static analysis
No suspicious patterns detected.