Resources

PayloadsAllTheThings/Upload Insecure Files at master · swisskyrepo/PayloadsAllTheThingsGitHub

Unrestricted File Upload | OWASP Foundation

Bypass file upload filter with .htaccess

Unrestricted File Upload TestingAptive

Bypassing File Upload RestrictionsPenetration Testing Lab

File UploadHackTricks

Unrestricted File Upload In PHPMedium