🔒 Fix XML External Entity (XXE) Vulnerability

[ManupaKDU]

🎯 What: The vulnerability fixed is an XML External Entity (XXE) Injection in Utilities/PersistentSettings.cs.
⚠️ Risk: The Load method parses an XML file from the filesystem. If left unfixed, an attacker could potentially supply a malicious XML payload (e.g. replacing the settings file or intercepting it) that resolves external entities. This could lead to arbitrary file disclosure or server-side request forgery (SSRF), posing a significant security risk.
🛡️ Solution: The fix sets the XmlResolver property of XmlDocument instances to null immediately after instantiation. This explicitly disables the resolution of external XML entities, eliminating the XXE vulnerability. The change is applied proactively to both the Load and Save methods for defense-in-depth.

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PR created automatically by Jules for task 3383492930856862791 started by @manupawickramasinghe

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