Lack of Duplicate Header Detection in `Secure` Class

[nitish-yaddala]

Description

If duplicate security headers are accidentally added (e.g., two different Content-Security-Policy definitions via custom headers and Secure defaults), they will be blindly overwritten or conflict during dictionary construction.

This may lead to:

• Weakened security policies if a less restrictive header is applied.
• Unintended behavior if multiple security settings silently collide.

Ensuring that only one definition per security header is enforced is critical for maintaining strong and predictable security controls.

Affected Code

• return {header.header_name: header.header_value for header in self.headers_list} — Line 223

Recommendation

• Detect and warn if multiple headers with the same name exist in headers_list before building the dictionary.
• Optionally:
  • Merge compatible headers where feasible (e.g., merging CSP directives instead of overwriting).
  • Allow users to explicitly control override behavior via configuration (e.g., a merge_duplicates flag).