fix(security): add DOMPurify sanitization to prevent XSS in MarkdownView

[arjanchaudharyy]

Issue
When rendering markdown content in the
MarkdownView
component, user-provided content was being inserted directly into the DOM using dangerouslySetInnerHTML without sanitization. This created a Stored XSS vulnerability where attackers could inject malicious scripts that execute when other users view the content.

Attack Vectors:

Script tag injection: <script>stealCookies()</script>
Event handler injection:
JavaScript URL injection: link
Malicious iframe embedding from untrusted domains

Solution
Integrated DOMPurify (v3.2.4) for robust HTML sanitization before rendering
Implemented strict allowlist of safe HTML tags and attributes
Added custom hooks to validate iframe sources against trusted domains (YouTube, Vimeo only)
Added custom hooks to block javascript:, vbscript:, and data: URLs
Added comprehensive security test suite with 25+ test cases

[chatgpt-codex-connector]

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