Hit all forms (search, registration, contact, password reset, comment) with polyglot strings
Scan those functions with Burp's built-in scanner
Check cookie behavior across login/logout/timeout cycles
Perform user enumeration checks
Test password reset flows (plaintext?
URL token? reusable?)
Rotate numeric account identifiers in URLs
Test sensitive functions for IDOR, auth bypass, CSRF, HTTP downgrade
Directory brute with SecLists top short list
Test upload functions for executable file types