[buuctf] [geek challenge 2019] secret file

Open the topic

  No idea , So look at the source code

  See a hyperlink

Click in

 

  Click the button in the middle

be aware url Medium end.php

 

  Go back to the previous page , Click Open Web page source code

  What we need action.php

So try to use bp Grab the bag and see if you can catch it

  stay action.php You can see a response in the   secr3t.php 

So look at this page

  The Chinese prompt is obvious , But this code shows that something is filtered , I have to use php://filter

complete payload

secr3t.php?file=php://filter/read=convert.base64-encode/resource=flag.php

  Conduct base64 Decrypt it