🛡️ Sentinel: [HIGH] Fix path traversal vulnerabilities

[thirdeyenation]

🚨 Severity: HIGH
💡 Vulnerability: Used str.startswith() for path containment checks (if not str(target_file).startswith(str(self.base_dir)):) and Path.relative_to in try-except block, which are flawed for path traversal prevention. str.startswith allows accessing files like /base_dir_suffix when base_dir is /base_dir.
🎯 Impact: An attacker could bypass path restrictions to access sensitive files on the filesystem by exploiting prefix matching.
🔧 Fix: Updated code to use Path.is_relative_to(base_dir) to correctly ensure paths are safely constrained to the allowed base directory.
✅ Verification: Verified using python script that tests path resolution out of bounds and in bounds.

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PR created automatically by Jules for task 1725061449511023628 started by @thirdeyenation

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