diff --git a/documentation/security-testing-status.md b/documentation/security-testing-status.md
new file mode 100644
index 0000000..2f0fd53
--- /dev/null
+++ b/documentation/security-testing-status.md
@@ -0,0 +1,157 @@
+# Security Testing Status
+
+Tracking security testing progress and remaining tasks.
+
+---
+
+## Completed Testing
+
+### Local Fuzzer (tests/fuzz/run_fuzz.py)
+
+| Phase | Tests | Status |
+|-------|-------|--------|
+| Reconnaissance | 25 endpoints probed | PASS |
+| Input Fuzzing | Binary, unicode, size limits | PASS |
+| Injection Attacks | SQLi, XSS, SSTI, command injection | PASS |
+| Auth/Authz | Header spoofing, privilege escalation | PASS |
+| Business Logic | Burn-after-read, expiry, dedup | PASS |
+| Cryptography | PoW token replay, timing | PASS |
+
+### Production Fuzzer (mymx.me/paste)
+
+| Phase | Tests | Status |
+|-------|-------|--------|
+| Content Fuzzing | Null bytes, unicode, 50KB, control chars | PASS |
+| Injection Testing | SQLi, SSTI, XSS, command, path traversal | PASS |
+| Header Injection | Host override, XFF chains, SQLi in headers | PASS |
+| Path Fuzzing | Traversal, URL encoding, long paths | PASS |
+| MIME Detection | GIF+JS, PNG+HTML, PDF+HTML polyglots | PASS |
+
+### MIME Detection (Polyglot Attacks)
+
+| Attack Vector | Payload | Result |
+|---------------|---------|--------|
+| PNG + HTML | Magic bytes + script tag | Served as image/png |
+| GIF + JavaScript | GIF89a + JS comment trick | Served as image/gif |
+| PDF + ZIP | PDF header + ZIP trailer | Served as application/pdf |
+| SVG + Script | XML with embedded script | Served as text/plain |
+| JPEG + PHP | JFIF + PHP code | Served as image/jpeg |
+
+---
+
+## Remaining Tasks
+
+### MIME Detection - Additional Formats
+
+33 signatures untested on production:
+
+```
+[ ] WebP (image/webp)
+[ ] TIFF (image/tiff)
+[ ] BMP (image/bmp)
+[ ] ICO (image/x-icon)
+[ ] AVIF (image/avif)
+[ ] HEIC (image/heic)
+[ ] WebM (video/webm)
+[ ] MP4 (video/mp4)
+[ ] AVI (video/x-msvideo)
+[ ] MOV (video/quicktime)
+[ ] MKV (video/x-matroska)
+[ ] MP3 (audio/mpeg)
+[ ] WAV (audio/wav)
+[ ] FLAC (audio/flac)
+[ ] OGG (audio/ogg)
+[ ] WASM (application/wasm)
+[ ] 7z (application/x-7z-compressed)
+[ ] RAR (application/vnd.rar)
+[ ] TAR (application/x-tar)
+[ ] XZ (application/x-xz)
+[ ] BZ2 (application/x-bzip2)
+[ ] DMG (application/x-apple-diskimage)
+[ ] ISO (application/x-iso9660-image)
+[ ] DEB (application/vnd.debian.binary-package)
+[ ] RPM (application/x-rpm)
+[ ] CAB (application/vnd.ms-cab-compressed)
+[ ] DOCX (application/vnd.openxmlformats...)
+[ ] XLSX (application/vnd.openxmlformats...)
+[ ] PPTX (application/vnd.openxmlformats...)
+[ ] ODF (application/vnd.oasis.opendocument...)
+[ ] Java class (application/java-vm)
+[ ] Mach-O (application/x-mach-binary)
+[ ] AR archive (application/x-archive)
+```
+
+### Fuzzing Improvements
+
+```
+[ ] Add --target option to run_fuzz.py for external testing
+[ ] Implement adaptive rate limiting in production fuzzer
+[ ] Add hypothesis property-based tests for MIME detection
+[ ] Create polyglot generator for automated MIME confusion testing
+[ ] Add timing attack tests for authentication endpoints
+```
+
+### Penetration Testing (from PENTEST_PLAN.md)
+
+```
+[ ] Race condition: Burn-after-read via HEAD then GET
+[ ] Race condition: Content hash deduplication counter
+[ ] DoS: Memory exhaustion via unique IP rate limits
+[ ] DoS: Anti-flood list growth under load
+[ ] CLI: Clipboard command injection validation
+[ ] CLI: Certificate file permission exposure
+```
+
+### Documentation
+
+```
+[ ] Add remaining MIME test results to security assessment
+[ ] Document rate limiting behavior under attack
+[ ] Create threat model diagram
+[ ] Add security headers audit to CI pipeline
+```
+
+---
+
+## Test Commands
+
+```bash
+# Local fuzzer (starts isolated server)
+./venv/bin/python tests/fuzz/run_fuzz.py --verbose
+
+# Quick smoke test
+./venv/bin/python tests/fuzz/run_fuzz.py --quick
+
+# Specific phases only
+./venv/bin/python tests/fuzz/run_fuzz.py --phases 1,2,3
+
+# Hypothesis tests (via pytest)
+./venv/bin/pytest tests/test_fuzz.py -v
+
+# Production fuzzer (rate limited)
+python /tmp/prod_fuzz.py
+```
+
+---
+
+## Security Controls Verified
+
+| Control | Implementation | Verified |
+|---------|----------------|----------|
+| X-Content-Type-Options | nosniff | Yes |
+| Content-Security-Policy | default-src 'none' | Yes |
+| X-Frame-Options | DENY | Yes |
+| Magic byte detection | First 16 bytes, 42 signatures | Yes |
+| Input sanitization | Werkzeug header handling | Yes |
+| SQL injection prevention | SQLAlchemy parameterized queries | Yes |
+| SSTI prevention | No user content in templates | Yes |
+| Path traversal prevention | ID validation regex | Yes |
+
+---
+
+## Notes
+
+- Production testing requires rate limit awareness (1.5s+ delay)
+- X-SSL-Client-SHA1 spoofing requires TRUSTED_PROXY_SECRET in production
+- /metrics endpoint intentionally exposed for Prometheus
+- Hypothesis tests use Flask test client (in-memory, not network)