- Fix SQL injection vulnerability in migrateHash() by using prepared statements
- Add null/empty check in password_type() to prevent array access error
- Remove dead code branch in generateAuthHash() (unreachable $_SESSION check)
- Fix PHP version in error message (5.3 -> 5.5 for password_hash)
- Prevent username enumeration by using consistent error messages
- Fix spacing inconsistency in substr() call
- Add TODO comment about MD5 hash weakness
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>