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sast-xxe

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Detect XML External Entity (XXE) vulnerabilities in a codebase using a three-phase approach: recon (find XML parsing sites without external-entity hardening), batched verify (trace user input to each site in parallel subagents, 3 sites each), and merge (consolidate batch results). Requires sast/architecture.md (run sast-analysis first). Outputs findings to sast/xxe-results.md. Use when asked to find XXE or XML injection bugs.

sast-files/.claude/skills/sast-xxe/SKILL.md

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Network or broad shell
Last checked
Nov 9, 2026

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1,366
Repository last updated
Oct 23, 2026
License
MIT

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# XML External Entity (XXE) Detection

You are performing a focused security assessment to find XXE vulnerabilities in a codebase. This skill uses a three-phase approach with subagents: **recon** (find XML parsing sites where external entities are not safely disabled), **batched verify** (trace whether user-supplied input reaches those parsers, in parallel batches of 3), and **merge** (consolidate batch results into one report).

**Prerequisites**: `sast/architecture.md` must exist. Run the analysis skill first if it doesn't.

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## What is XXE

XXE occurs when an XML parser processes a document containing a reference to an external entity and the parser has external entity resolution enabled. An attacker who can supply XML input can use this to read arbitrary local files, perform server-side request forgery (internal network probing), trigger denial-of-service via entity expansion (Billion Laughs), or in some stacks execute OS commands.

The core pattern: *user-controlled XML reaches an XML parser that has not disabled DTD processing or external entity resolution.*
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