CVE-2023-28459: pretalx vulnerable to path traversal in HTML export

The commit diff shows critical security checks were added to both functions:

1. In dump_content: Added path.resolve() and parent directory validation to prevent traversal
2. In get_mediastatic_content: Added path resolution and containment checks for MEDIA/STATIC_ROOT These changes directly address CWE-22 (Path Traversal). The Sonar blog explicitly describes how these functions processed attacker-controlled paths without proper validation, enabling file read/write primitives. The vulnerability documentation and patch context leave no ambiguity about their role in the exploit chain.