Differential Security Review
Security-focused code review for PRs, commits, and diffs.
Core Principles
- Risk-First: Focus on auth, crypto, value transfer, external calls
- Evidence-Based: Every finding backed by git history, line numbers, attack scenarios
- Adaptive: Scale to codebase size (SMALL/MEDIUM/LARGE)
- Honest: Explicitly state coverage limits and confidence level
- Output-Driven: Always generate comprehensive markdown report file
Codebase Size Strategy
| Codebase Size | Strategy | Approach |
|---|---|---|
| SMALL (<20 files) | DEEP | Read all deps, full git blame |
| MEDIUM (20-200) | FOCUSED | 1-hop deps, priority files |
| LARGE (200+) | SURGICAL | Critical paths only |
Risk Level Triggers
| Risk Level | Triggers |
|---|---|
| HIGH | Auth, crypto, external calls, value transfer, validation removal |
| MEDIUM | Business logic, state changes, new public APIs |
| LOW | Comments, tests, UI, logging |
Workflow Overview
Pre-Analysis → Phase 0: Triage → Phase 1: Code Analysis → Phase 2: Test Coverage
↓ ↓ ↓ ↓
Phase 3: Blast Radius → Phase 4: Deep Context → Phase 5: Adversarial → Phase 6: ReportPhase Summaries
Phase 0: Triage
- Classify files by risk level
- Identify HIGH risk files for deep analysis
Phase 1: Code Analysis
- Git blame on removed security code
- Analyze changes for security implications
Phase 2: Test Coverage
- Check if security-critical changes have tests
- Flag missing tests as elevated risk
Phase 3: Blast Radius
- Calculate how many callers are affected
- High blast radius + HIGH risk = immediate escalation
Phase 4: Deep Context
- For HIGH risk changes, build full context
- Trace data flow, understand invariants
Phase 5: Adversarial
- Model attacker perspective
- Develop concrete exploit scenarios
- Rate exploitability
Phase 6: Report
- Generate comprehensive markdown report
- Include all findings with file:line references
Red Flags (Stop and Investigate)
Immediate escalation triggers:
- Removed code from "security", "CVE", or "fix" commits
- Access control modifiers removed (onlyOwner, internal → external)
- Validation removed without replacement
- External calls added without checks
- High blast radius (50+ callers) + HIGH risk change
These patterns require adversarial analysis even in quick triage.
Rationalizations (Do Not Skip)
| Rationalization | Why It's Wrong | Required Action |
|---|---|---|
| "Small PR, quick review" | Heartbleed was 2 lines | Classify by RISK, not size |
| "I know this codebase" | Familiarity breeds blind spots | Build explicit baseline context |
| "Git history takes too long" | History reveals regressions | Never skip Phase 1 |
| "Just a refactor, no security impact" | Refactors break invariants | Analyze as HIGH until proven LOW |
Quality Checklist
Before delivering:
- All changed files analyzed
- Git blame on removed security code
- Blast radius calculated for HIGH risk
- Attack scenarios are concrete (not generic)
- Findings reference specific line numbers + commits
- Report file generated
When NOT to Use
- Greenfield code (no baseline to compare)
- Documentation-only changes
- Formatting/linting changes
- User explicitly requests quick summary only
Attribution
Based on trailofbits/skills differential-review skill - 45+ installs.