[buuctf] [actf2020 freshman competition]include

There's a question ‘tips’ link , Click on

according to url Medium flag.php And a hint of the title , It should be conceivable that the file contains ,flag stay flag.php in , So I thought of using PHP Fake protocol

structure payload:

?file=php://filter/read=convert.base64-encode/resource=flag.php

  So you get the base64 Encrypted content , Just decrypt it