Path Traversal Protection Found Incomplete in Backend Server — URL Encoding Bypass Unguarded

A security audit has identified a significant gap in path traversal defenses within `backend/server.js`. The file operations module at lines 176-218 currently implements only basic pattern matching for parent directory traversal sequences (`../` and `..\`), leaving the system potentially vulnerable to Unicode and URL encoding bypass techniques. The vulnerability has been classified under CWE-22 (Path Traversal), a well-established weakness that could allow attackers to access files outside intended directories by manipulating file path inputs.

The current implementation fails to account for encoded representations of traversal sequences. Attackers could exploit this by supplying URL-encoded or Unicode-encoded versions of `../` to circumvent the existing filters. This oversight means that files beyond the application's intended scope—including sensitive configuration files, credentials, or system data—could be exposed or manipulated through specially crafted requests. The issue has been flagged as high priority, underscoring the urgency of addressing the gap before potential exploitation.

The implications extend beyond individual file exposure. If left unpatched, this vulnerability could serve as an entry point for more sophisticated attacks, potentially compromising entire backend infrastructure. Organizations relying on similar pattern-matching approaches are advised to review their own implementations for equivalent weaknesses. A comprehensive path traversal prevention strategy would need to normalize all encoding variants before applying validation, ensuring that no escaped or encoded sequences can bypass security controls.