/finding-discovery

name: finding-discovery
description: Use when Codex is already in the finding-discovery phase of a security scan or the user explicitly asks to discover candidate security findings in a repository or code change. Do not use as the primary trigger for full PR, commit, branch, patch, or repository scans.

Security Finding Discovery

Objective

Investigate the proposed code or code changes for technically plausible security vulnerabilities using the threat model as context.

Standard and Deep discovery workers follow their self-contained coordinator prompts; they do not invoke this skill. For an explicit standalone repository-discovery request, apply the relevant checklist below directly to the authorized current source without running the diff-only workflow or starting another scan.

Artifact Resolution

The path references in this skill are the default locations for this phase. If the user explicitly provides a different path for a required input or output, use the user-provided path instead of the corresponding default path referenced in this skill. If a required input is still missing, stop and ask the user for it before continuing. Use the shared scan artifact path conventions in `../../references/scan-artifacts.md`.

SECURITY.md Guidance Gate

Read `../../references/security-guidance.md` and resolve the applicable policy before inspecting each source file. A delegated file-review worker must do the same before reading its assigned source.

Compact Diff Workflow

When a running diff scan already supplies its file inventory through `list_codex_security_review_items`, review that inventory directly and record all candidates once with `record_codex_security_discovery_candidates`. Do not generate ranked worklists, per-finding ledgers, discovery receipts, or discovery reports. Skip the legacy workflow and artifact requirements below.

Code Diff Workflow

For a targeted code diff without an existing compact inventory:

• Read `../security-scan/references/scan-artifacts-and-ledger.md`.
• Generate `rank_input.jsonl` deterministically from changed source-like files with `<python_command> <plugin_dir>/scripts/generate_rank_input.py make-diff-rank-input --repo <repo_root> --base <base> --mode revisions --head <head> --out <discovery_dir>/rank_input.jsonl` for PR, commit, and branch diffs, or `<python_command> <plugin_dir>/scripts/generate_rank_input.py make-diff-rank-input --repo <repo_root> --base <base> --mode local-patch --out <discovery_dir>/rank_input.jsonl` for a local patch.
• Copy every diff row into `deep_review_input.jsonl` with `<python_command> <plugin_dir>/scripts/generate_rank_input.py copy-deep-review-input --rank-input <discovery_dir>/rank_input.jsonl --out <discovery_dir>/deep_review_input.jsonl`. Diff scans do not rank or drop changed files before deep review.
• Add directly supporting files required to understand the changed security behavior only when repository evidence shows they are needed. Do not use them to broaden into unrelated repository-wide enumeration.
• Deep-review every file in `deep_review_input.jsonl` using the shared scoped file-review rules.
• Stay anchored to the changed code and directly supporting files. Unchanged siblings are context or negative controls unless the diff newly reaches them, weakens their shared control, or changes a shared sink/helper they depend on.
• When the diff is too large to review credibly as one parent-agent pass, use file-review subagents when they are available under the resolved scan authorization and follow the shared scoped deep-review rules in `../security-scan/references/scan-artifacts-and-ledger.md#scoped-deep-review`.

Discovery Checklist

Use this checklist to keep discovery specific without turning it into validation or attack-path analysis:

• Use tools to inspect the changed files and the minimum supporting files they rely on before deciding anything.
• Treat the commit message and title as potentially incomplete or misleading; trust the actual code path more than the narrative.
• Follow the entire changed-code chain far enough to understand how the diff affects authorization, trust boundaries, dangerous sinks, or security controls.
• Prefer multiple distinct finding families only when they come from different root causes; do not split one issue into cosmetic variants, but keep independently reachable instances as separate candidate entries.
• When the diff changes a shared helper, guard, route pattern, template pattern, or sink wrapper, expand to sibling call sites that the changed code directly affects, and keep each vulnerable instance addressable.
• Look for attacker-controlled input, broken enforcement, or dangerous sinks introduced or made reachable by the change.
• Stay anchored to the diff and the supporting files it depends on rather than drifting into unrelated repository scanning.
• For advisory-seeded repository-wide and scoped-path scans, keep any supplied advisory row id, exact file, line, source, sink, or broken-control hint visible in the candidate ledger. A neighboring same-CWE finding can be an additional candidate, but it does not satisfy the seeded row unless it covers the same vulnerable control and effect.
• Do not group many vulnerable files under one candidate when the files have separate line-level source/sink/control evidence.
• When a dangerous sink has multiple call sites, enumerate each call site with its own source and closest control.
• When repeated templates, query builders, parser operations, auth/object endpoints, or shared-helper callers are independently reachable, keep each vulnerable file and sink/control line as its own candidate instance even if the final report later groups related prose.
• When source/sink evidence crosses a wrapper into a shared sink/control helper, include both locations in the candidate so validation can test reachability without losing the root vulnerable line.
• When a concrete operation, strategy, converter, validator, or han