OWASP Security

Apply these standards when writing or reviewing code. For a review, follow the workflow below.

Reference files (read the one the task needs, and only the section you need):

• reference/review-checklist.md: coverage checklist for every Top 10 category, plus LLM and agent checks. Read during step 3 of a review.
• reference/languages.md: per-language pitfalls with unsafe/safe examples for 20+ languages. Read the section for the language under review.
• reference/config-and-supply-chain.md: A02 and A03 in Dockerfiles, Kubernetes, Terraform, framework config, security headers, lockfiles, and CI/CD. Read when the change touches config, IaC, dependencies, or pipelines.
• reference/owasp-report.md: attack vectors, mitigations, and worked examples for every Top 10:2025, ASVS 5.0, LLM Top 10, and Agentic item. About 1100 lines: jump to the section you need.

Security Review Workflow

Copy this checklist into your response and tick it off as you go:

Security Review Progress:
- [ ] Step 1: Map entry points and trust boundaries
- [ ] Step 2: Load the references this code needs
- [ ] Step 3: Sweep for candidate issues
- [ ] Step 4: Triage every candidate
- [ ] Step 5: Report findings

Step 1: Map entry points and trust boundaries. List where attacker-controlled data enters: routes and handlers, headers and cookies, uploads, webhooks, queue consumers, CLI arguments, third-party API responses, and anything an LLM reads or returns. Note where authentication and authorization are enforced; it is often centralized in middleware rather than per route.

Step 2: Load the references this code needs. The language section of languages.md; config-and-supply-chain.md if config, IaC, dependencies, or CI changed; the LLM and Agentic sections of owasp-report.md if the code calls a model or runs an agent.

Step 3: Sweep for candidate issues. Walk review-checklist.md for the categories the code touches. For each candidate, trace the path from an entry point in step 1 to the sink.

Step 4: Triage every candidate with the rubric in "Before Reporting a Finding" below. Drop candidates that fail it, or downgrade them to defense-in-depth. If a candidate's reachability is unclear, go back to step 1 for that input before deciding.

Step 5: Report findings in the format below, highest severity first.

Before Reporting a Finding

A pattern match is not a vulnerability. The most common failure mode in automated security review is reporting unreachable or already-mitigated code, which buries the real findings. Confirm all four before reporting:

1. Is the input actually attacker-controlled? Trace it back to a real entry point: a request parameter, header, cookie, uploaded file, webhook, queue message, or third-party API response. A value that only ever comes from a constant, an enum, or trusted internal config is not an injection source.
2. Is the sink reachable with that input? Check whether validation, an allowlist, an ORM, or a framework-level control already sits between them. Look for auth middleware (middleware.ts, proxy.ts, Express/Django/Rails middleware, a base controller, decorators) before flagging a route as missing authorization. Enforcement is often centralized rather than per-route.
3. What is the blast radius? Who can trigger it, what do they get, and does it cross a trust boundary? An SSRF reaching cloud metadata differs from one reaching localhost only.
4. Can the attacker perform every step? Each step of the exploit must be possible from the attacker's position. A symlink race needs a way to create symlinks on the server; a header attack needs a client that can set that header. If a step needs a capability the code doesn't show the attacker having, the finding is "Needs verification", not High.

Report severity by exploitability, not by pattern. State the concrete path (this input reaches this sink) and say so explicitly when a finding is theoretical or defense-in-depth rather than directly exploitable. If reachability can't be determined from the code available, say that instead of asserting either way.

Reporting Format

One block per finding, highest severity first:

[SEVERITY] Title (CWE-###, OWASP A##:2025, LLM## Risk Name, ASI## Risk Name)
Location:   path/to/file.ext:LINE
Path:       <entry point> -> <intermediate hops> -> <sink>
Impact:     who can trigger it, what they get, which trust boundary it crosses
Fix:        the concrete change, with a code snippet when it isn't obvious
Confidence: Confirmed | Likely | Needs verification (say what you couldn't see)

Write every LLM and ASI ID with its risk name, e.g. "LLM03 Excessive Agency". A bare LLM ID is ambiguous: the 2025 and 2026 editions use the same numbers for different risks.

Severity	Meaning
Critical	Unauthenticated remote code execution, auth bypass, or mass data exposure
High	Authenticated exploitation crossing a trust boundary (IDOR into other tenants, SQLi behind login)
Medium	Needs unusual preconditions, or impact is limited to the attacker's own data
Low	Defense-in-depth gap with no demonstrated exploit path
Info	Hardening suggestion; say plainly that it is not a vulnerability

If the review finds nothing exploitable, say so directly. Do not pad the report with Info items to look thorough; a long list is what makes real findings get ignored.

OWASP Top 10:2025

Three categories were renamed from 2021 and two are new (A03, A10). Use these names and numbers; much OWASP material online still cites the 2021 list.

#	Category	Key Prevention
A01	Broken Access Control (now includes SSRF)	Deny by default, enforce server-side, verify ownership
A02	Security Misconfiguration	Harden configs, disable defaults, minimize features
A03	Software Supply Chain Failures	Lock versions, verify integrity, audit dependencies
A04	Cryptographic Failures	TLS 1.2+, AES-256-GCM, Argon2/bcrypt for passwords
A05	Injection	Parameterized queries, input validation, safe APIs
A06	Insecure Design	Threat model, rate limit, design security controls
A07	Authentication Failures	MFA, check breached passwords, secure sessions
A08	Software or Data Integrity Failures	Sign packages, SRI for CDN, safe serialization
A09	Security Logging and Alerting Failures	Log security events, structured format, alerting
A10	Mishandling of Exceptional Conditions	Fail-closed, hide internals, log with context

OWASP Top 10 for LLM Applications (2026)

For applications that call LLMs (chatbots, RAG, copilots, agents). The 2026 edition renumbered the list; translate 2025 IDs with the table in owasp-report.md and cite 2026 IDs only.

#	Risk	Key Mitigation
LLM01	Prompt Injection	No complete fix exists. Fence untrusted content (including images, audio, tool output), keep privileges out of the model's reach, filter outputs
LLM02	Sensitive Information Disclosure	Sanitize training/RAG data, strip PII from context, restrict what the model can retrieve per user
LLM03	Excessive Agency	Minimize tools and permissions, require human approval for destructive actions, scope credentials per task
LLM04	Supply Chain	Verify model provenance and signatures, vet third-party model hubs, lock model + adapter versions
LLM05	Data and Model Poisoning	Validate training/fine-tuning sources, anomaly-detect on data ingestion, hold-out integrity tests
LLM06	Unbounded Consumption	Rate-limit per user/key, cap tokens and tool calls per request, monitor cost, set hard timeouts
LLM07	Misinformation	Cite sources, surface confidence, require grounding for high-stakes answers, disclose AI provenance
LLM08	Hidden Context Exposure	Assume the system prompt, tool schemas, and other hidden context are extractable: no secrets there, and no authorization or policy that relies on them staying hidden
LLM09	Vector and Embedding Weaknesses	Tenant-isolate vector stores, access-control on retrieval, sign or hash chunks against indirect prompt injection
LLM10	Improper Output Handling	Treat all LLM output, including generated code, as untrusted input: validate, escape, or sandbox before any sink (SQL, shell, HTML, code, tool calls)

OWASP Top 10 for Agentic Applications (2026)

For AI agent systems that plan, call tools, or keep memory:

Risk	Description	Mitigation
ASI01: Agent Goal Hijack	Prompt injection alters agent objectives	Treat tool and retrieved content as data, goal boundaries, behavioral monitoring
ASI02: Tool Misuse & Exploitation	Tools used in unintended ways	Least privilege, fine-grained permissions, validate I/O
ASI03: Identity & Privilege Abuse	Delegated trust, inherited credentials, role chain exploits	Short-lived scoped tokens, identity verification
ASI04: Agentic Supply Chain Vulnerabilities	Compromised plugins/MCP servers	Verify signatures, sandbox, allowlist plugins
ASI05: Unexpected Code Execution	Unsafe code generation/execution	Sandbox execution, static analysis, human approval
ASI06: Memory & Context Poisoning	Corrupted RAG/context data	Validate stored content, segment by trust level
ASI07: Insecure Inter-Agent Communication	Spoofing/intercepting agent-to-agent messages	Authenticate, encrypt, verify message integrity
ASI08: Cascading Failures	Errors propagate across systems	Circuit breakers, graceful degradation, isolation
ASI09: Human-Agent Trust Exploitation	Over-trust in agents leveraged to manipulate users	Label AI content, user education, verification steps
ASI10: Rogue Agents	Compromised agents acting maliciously	Behavior monitoring, kill switches, anomaly detection

ASVS 5.0 Key Requirements

ASVS 5.0 (May 2025) renumbered and reorganized every chapter. 4.0 requirement IDs do not map to 5.0 — V2.1.1 meant "password length" in 4.0 and means something else now. Cite 5.0 IDs only. Levels are defined by share of requirements, not by application category:

Level	Share	Intent
L1	~20%	Minimum bar; deliberately small to lower the barrier to entry
L2	~50% (≈70% cumulative)	What most applications should target
L3	remaining ~30%	Highest assurance

Level 1 — the minimum bar

• Passwords at least 8 characters; 15+ strongly recommended (6.2.1)
• No composition rules — permit any characters, paste, and password managers (6.2.5, 6.2.7)
• Block at least the top 3000 common passwords (6.2.4)
• Anti-automation against credential stuffing and brute force (6.3.1)
• No default accounts like root/admin/sa (6.3.2)
• Reference session tokens from a CSPRNG with 128+ bits entropy (7.2.3)
• New session token issued on authentication and re-authentication (7.2.4)
• Session fully unusable after logout or expiry (7.4.1)
• Function-level and data-level access restricted to explicit permissions (8.2.1, 8.2.2)
• Authorization enforced at a trusted service layer the client cannot manipulate (8.3.1)
• Parameterized queries / ORM for all data access (1.2.4); parameterized OS calls (1.2.5)
• Context-appropriate output encoding for HTML, URLs, and JavaScript/JSON (1.2.1–1.2.3)
• Avoid eval() and dynamic code execution (1.3.2)
• Input validated at a trusted service layer, positive/allowlist where possible (2.2.1, 2.2.2)
• TLS 1.2+ on all external traffic, publicly trusted certificates (12.1.1, 12.2.1, 12.2.2)
• Approved ciphers and modes only — no ECB, no PKCS#1 v1.5 padding (11.3.1, 11.3.2)
• No sensitive data in URLs or query strings (14.2.1)

Level 2 — what most applications should target

• MFA, or a documented combination of single factors (6.3.3)
• Passwords checked against a breached-password set (6.2.12)
• No forced periodic password rotation — rotate only on compromise (6.2.10)
• All security logging starts here. ASVS 5.0 has no L1 logging requirements; the whole of V16 is L2+. Log authentication attempts, failed authorization, security events, and unexpected errors (16.3.1–16.3.4)
• Log entries carry when/where/who/what metadata on a synchronized clock (16.2.1, 16.2.2)
• Logs encoded against log injection, protected from modification, shipped off-box (16.4.1–16.4.3)
• Generic error message to the user; detail stays in the log (16.5.1)

Level 3 — highest assurance

ASVS 5.0 has 92 L3 requirements; they are not enumerated here. Two worth knowing because they tighten an L2 requirement rather than adding a new one:

• One factor must be hardware-based and phishing-resistant, e.g. a FIDO key (6.3.3, L3 clause)
• Log all authorization decisions, not only failures (16.3.2, L3 clause)

For an actual L3 assessment, work from the standard itself — see reference/owasp-report.md for the chapter map.