Security audit

Harness Writing

Security checks for vulnerabilities and agentic risk

Overview

This skill is a documentation-only fuzzing-harness guide with some imperfect sample code, but no hidden execution, persistence, or data access behavior.

Reasonable to install as a fuzzing reference. Before copying the C++ examples into production fuzz targets, replace raw typed-pointer casts with memcpy or explicit decoding, and prefer vector::data() plus clear zero-length handling for vector-backed inputs.

A.I.G

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 (2)

T09 · Insecure Skill Coding Practices

Warning

Location: SKILL.md:120
Finding: Undefined Behavior from Unaligned and Aliasing-Violating Integer Reads
Content: View full analysis
Remediation: View remediation
(data[0]) | (static_cast(data[1]) << 8) | (static_cast(data[2]) << 16) | (static_cast(data[3]) << 24); ``` Update the quick-reference entry and every repeated example so agents are not encouraged to reproduce the unsafe form. Compile sample harnesses with AddressSanitizer and UndefinedBehaviorSanitizer to validate the corrected guidance. ]]>

T09 · Insecure Skill Coding Practices

Warning

Location: SKILL.md:139
Finding: Potential Empty-Vector Dereference in FuzzedDataProvider Examples
Content: View full analysis
str1 = fuzzed_data.ConsumeBytesWithTerminator(32, 0xFF); std::vector str2 = fuzzed_data.ConsumeBytesWithTerminator(32, 0xFF); ``` ### Technical Analysis The examples use `&str1[0]` and `&str2[0]` without first proving that the vectors are nonempty. Calling `operator[]` with index zero on an empty `std::vector` is outside its valid element range and results in undefined behavior. Fuzzing naturally exercises empty and truncated inputs, so an empty-vector state must be treated as an expected condition. A harness-originated invalid access undermines the document's stated requirement that the harness handle malformed and small inputs gracefully. Using `vector::data()` avoids invoking `operator[]` on an empty vector. The target API must still define how it handles a zero-length input and the pointer value associated with it. ### Attack Path 1. A developer or agent copies the documented `FuzzedDataProvider` harness. 2. The fuzzer supplies data from which one of the vectors is empty. 3. The harness evaluates `str1[0]` or `str2[0]` while preparing arguments for `concat`. 4. The out-of-range access invokes undefined behavior before or during the target call. 5. The campaign records a misleading crash, repeatedly explores a harness defect, or fails to reach the intended system-under-test logic. This is an indirect risk in harnesses created from the guidance; the Markdo ...[truncated 421 chars]
Remediation: View remediation

SkillSpector

Vulnerability Patterns

Prompt InjectionInstruction Override, Hidden Instructions, Exfiltration Commands
Data ExfiltrationExternal Transmission, Env Variable Harvesting, File System Enumeration
Privilege EscalationExcessive Permissions, Sudo/Root Execution, Credential Access
Supply ChainUnpinned Dependencies, External Script Fetching, Obfuscated Code
Excessive AgencyUnrestricted Tool Access, Autonomous Decision Making, Scope Creep

Static analysis

No suspicious patterns detected.