🛡️ Sentinel: [CRITICAL] Fix path traversal in ApiFilesGet

[thirdeyenation]

🚨 Severity: CRITICAL
💡 Vulnerability: The API endpoint api_files_get.py allowed arbitrary file reading via path traversal (e.g., ../../../etc/passwd) and unrestricted absolute paths, failing to validate user-supplied file paths against the application base directory.
🎯 Impact: An attacker could read arbitrary files on the host system, including sensitive configuration files, environment variables, or private keys, leading to complete system compromise or data exfiltration.
🔧 Fix: Added a strict validation check using files.is_in_base_dir(external_path) to ensure the resolved file path always stays within the application's base directory boundaries. Paths outside this directory are denied access.
✅ Verification: Wrote a test script to verify that requests for files outside the base directory via absolute paths or path traversal (/a0/../../..) are explicitly blocked and return no data, while valid files within the base directory are returned successfully.

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PR created automatically by Jules for task 13876370999991279021 started by @thirdeyenation

[google-labs-jules]

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