CB exploiting-mass-assignment-in-rest-apis
Discovers and exploits mass assignment (autobinding) in REST APIs by injecting unexpected or hidden parameters (e.g. role, isAdmin, plan) into create/update requests, using Burp Suite Intruder, Arjun, and param-miner to find bindable fields on ORM-backed endpoints (Rails, Django, Laravel, Spring). Use when testing REST APIs for privilege escalation or authorization bypass via unintended parameter binding.
Discovers and exploits mass assignment (autobinding) in REST APIs by injecting unexpected or hidden parameters (e.g. role, isAdmin, plan) into create/update…
As a process B 67/100 · Nearly there — weak spots: when it triggers, failures and branches, running it twice
How to improve
- Your own cases (evals/evals.json, 4–6 real requests with expected answers): the full check would then run those instead of a model-drafted suite.
- A spec.yaml with trigger phrases and assertions — a behaviour contract for CI; `skilltest init` writes a template.
Guard findings · 7
✓ No critical or high findings
Medium and low: 7
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low Risky intent
intent-offensive-securityreferences/api-reference.md:13Offensive-security / dual-use content (legitimate for authorised testing; review intended use)| `role` / `isAdmin` | Privilege escalation |
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low Risky intent
intent-offensive-securitySKILL.md:8Offensive-security / dual-use content (legitimate for authorised testing; review intended use)REST APIs for privilege escalation or authorization bypass via unintended
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low Risky intent
intent-offensive-securitySKILL.md:42Offensive-security / dual-use content (legitimate for authorised testing; review intended use)- During bug bounty hunting on applications with CRUD API operations
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low Risky intent
intent-offensive-securitySKILL.md:77Offensive-security / dual-use content (legitimate for authorised testing; review intended use)### Step 2 — Test Privilege Escalation via Role Fields
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low Risky intent
intent-offensive-securitySKILL.md:216Offensive-security / dual-use content (legitimate for authorised testing; review intended use)1. **Admin Privilege Escalation** — Inject `"role":"admin"` or `"isAdmin":true` in profile update to gain administrative access
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low Risky intent
intent-offensive-securitySKILL.md:233Offensive-security / dual-use content (legitimate for authorised testing; review intended use)| 1 | PATCH /api/users/me | role | "user" | "admin" | Privilege Escalation |
A further 1 matches are quotations in this security skill's documentation and are not counted as findings.
Files scanned: 4. Evidence is masked. Grey chips explain why severity was lowered.
Against the Agent Skills spec
- note
frontmatter-keyunknown frontmatter key "domain" - note
frontmatter-keyunknown frontmatter key "subdomain" - note
frontmatter-keyunknown frontmatter key "nist_csf" - note
frontmatter-keyunknown frontmatter key "mitre_attack"
Process rating: all ten parameters 67/100
- 0Failures and branches. Linear process with no failure handling
- 0Progress reporting. Says nothing while it works
- 20When it triggers. No condition that starts the skill
- 30Running it twice. 1 mutating operations with no state check
- 60Result and completion. Output format stated, no completion criterion
- 70Inputs and preconditions. Inputs and preconditions are listed
- 100Tools and files. No external tools needed
- 100Steps. 16 steps
- 100Consistency. Name and required fields are in place
- 100Execution cost. Instruction body is 2139 tokens
Everything here is measured from the skill text rather than judged by a model, so the numbers are checkable. A parameter weighs more when it is a more common reason for the process to stall.
Quality signals
- +5Description has no quoted example phrases that should trigger the skill
- +4Description does not say when NOT to use the skill (false activations)
- -41 reference files, but SKILL.md never points to them: the model will not open them
- -31 of 1 scripts are never mentioned in SKILL.md
- +2Single-language instructions
- +3Description length 408: enough signal without eating the budget
- +4Structure: 14 headings
- +3Step-by-step instructions: 16 items
- +3Output format is stated explicitly
- +4Has examples (7 code blocks)
- +1License stated
Quality base 70; lint remarks subtract, signals add up to 100. Result: 78.