Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add ByamB4/find-cve-agent --skill method-clobberinggit clone --depth 1 https://github.com/ByamB4/find-cve-agentWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/byamb4/find-cve-agent/method-clobbering)<a href="https://agentmods.dev/skills/byamb4/find-cve-agent/method-clobbering"><img src="https://agentmods.dev/badge/skills/byamb4/find-cve-agent/method-clobbering/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/byamb4/find-cve-agent/method-clobbering"><img src="https://agentmods.dev/badge/skills/byamb4/find-cve-agent/method-clobbering.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00040 | $0.00994 |
| Opus 5 | $0.00020 | $0.00497 |
| Sonnet 5 | $0.00008 | $0.00199 |
| Haiku 4.5 | $0.00004 | $0.00099 |
Grade A, and why
method-clobbering scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 100 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Method Clobbering Detection
When to Use
Audit CSV/form/query string parsers that create plain objects from untrusted input where the attacker can control property names (keys), not just values.
Key Insight
When a parser creates a plain object {} from user input, the attacker can set keys like toString, valueOf, hasOwnProperty to non-function values. Any code that later calls these methods on the object will throw a TypeError.
Important: JSON.parse can do the same thing. You MUST show why the library-specific clobbering is worse than what JSON.parse enables. Show a REAL crash path, not just theoretical property overwrite.
Dangerous Keys
| Key | Normal Type | Effect When Clobbered |
|---|---|---|
toString |
Function | obj + "" throws TypeError |
valueOf |
Function | obj == x or coercion throws TypeError |
hasOwnProperty |
Function | obj.hasOwnProperty(k) throws TypeError |
constructor |
Function | Type checks fail |
__proto__ |
Object | Prototype pollution (see prototype-pollution skill) |
__defineGetter__ |
Function | Legacy getter/setter manipulation |
__defineSetter__ |
Function | Legacy getter/setter manipulation |
__lookupGetter__ |
Function | Legacy getter/setter introspection |
toJSON |
undefined | JSON.stringify(obj) throws TypeError |
then |
undefined | await obj or Promise.resolve(obj) treats obj as thenable |
Process
Step 1: Find Parsers That Create Objects
grep -rn "\[key\]\s*=" . --include="*.js" --include="*.ts"
grep -rn "\[header\]\|\[field\]\|\[name\]\|\[prop\]" .
grep -rn "result\[\|output\[\|obj\[\|data\[\|parsed\[" .
Step 2: Check If Keys Are User-Controlled
Common sources of attacker-controlled keys:
- CSV column headers (first row)
- HTTP form field names
- Query string parameter names
- Configuration file keys
- JSON object keys (but JSON.parse already handles this)
Step 3: Check for Key Filtering
grep -rn "Object\.create(null)" . # Null prototype = safe
grep -rn "hasOwnProperty\|toString\|valueOf" . | grep -i "filter\|block\|skip"
grep -rn "Object\.keys\|Map\|new Map" .
What ships with it
3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 9d ago First seen · 100 lines · 40 tokens per session scan A 58e43d6f4fc8
method-clobbering is a skill published in the GitHub repository ByamB4/find-cve-agent (48 stars, last pushed 5mo ago), licensed Apache-2.0. It adds 40 tokens to every session and 994 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other skills, from other repositories
wordpress-plugin-hunt
Hunt WP plugins via REST, exploit CVEs when version known.
deep-invade
Deep pentest WP: SSRF, plugin CVE, JS mine, port scan chain.
zimbra-attack
Zimbra SOAP user enum, CVE-2022-37042, SSRF when webmail.
wp-plugin-cve-hunt
Systematic approach to finding and testing CVEs for identified WordPress plugins. Covers plugin discovery, version extraction from multiple sources (readme.txt, assets, inline JS), CVE database cross-referencing with WPScan/Patchstack/NVD/NVD API, version-based vulnerability matching, exploitation PoC generation, and…
analyzing-sbom-for-supply-chain-vulnerabilities
Parses Software Bill of Materials (SBOM) in CycloneDX and SPDX JSON formats to identify supply chain vulnerabilities by correlating components against the NVD CVE database via the NVD 2.0 API. Builds dependency graphs, calculates risk scores, identifies transitive vulnerability paths, and generates compliance reports.…
bug-bounty-hunting
Hunt vulnerabilities like an expert, not a linear software engineer: come at a target from the overlooked angle, reason by analogy and transfer proven attack mechanisms, attack the hidden assumptions and the seams between systems, drill to the mechanism, then keep it honest with proof and persistence (acceptance !=…