Add PoC and reproduction instructions

README.md

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+# PoC: Joblib Compressed Pickle Bypasses ML Security Scanners
+
+**Format:** Joblib (.joblib)
+**Target:** PickleScan + ModelScan
+**CWE:** CWE-502 (Deserialization of Untrusted Data)
+
+## Vulnerability
+
+Joblib compressed pickles bypass both PickleScan and ModelScan. The scanners use `pickletools.genops()` which cannot parse compressed data, reporting files as clean. `joblib.load()` handles decompression and executes the embedded payload.
+
+## Reproduction
+
+```bash
+pip install picklescan modelscan
+picklescan -p poc_joblib_bypass.joblib  # Reports: Infected files: 0
+modelscan scan -p poc_joblib_bypass.joblib  # Reports: No issues found!
+python3 -c "import joblib; joblib.load('poc_joblib_bypass.joblib')"  # Executes payload
+```
+
+**Tested:** PickleScan 1.0.3, ModelScan 0.8.7