Penetration Testing Vulnarability Remediation

Need to fix the below vulnerabilities in the app

1. STORED CROSS SITE SCRIPTING
2. PRIVILEGE ESCALATION BY FORCEFUL BROWSING
3. SQL INJECTION
4. HTML INJECTION
5. SERVER SIDE SOURCE CODE LEAKAGE
6. CROSS-SITE REQUEST FORGERY
7. DIRECTORY LISTING
8. CSV INJECTION
9. BAD SECURITY CODE PRACTICE
10. MISCONFIGURED PHP CONFIGURATION
11. SERVER VERSION DISCLOSURE
12. SECURITY HEADER MISSING