Lab: Using application functionality to exploit insecure deserialization


This lab uses a serialization-based session mechanism. A certain feature invokes a dangerous method on data provided in a serialized object. To solve the lab, edit the serialized object in the session cookie and use it to delete the morale.txt file from Carlos's home directory.

You can log in to your own account using the following credentials: wiener:peter

You also have access to a backup account: gregg:rosebud


  1. Log in to your own account. On the "My account" page, notice the option to delete your account by sending a POST request to /my-account/delete.
  2. Send a request containing a session cookie to Burp Repeater.
  3. In Burp Repeater, study the session cookie using the Inspector panel. Notice that the serialized object has an avatar_link attribute, which contains the file path to your avatar.
  4. Edit the serialized data so that the avatar_link points to /home/carlos/morale.txt. Remember to update the length indicator. The modified attribute should look like this:

  5. Click "Apply changes". The modified object will automatically be re-encoded and updated in the request.
  6. Change the request line to POST /my-account/delete and send the request. Your account will be deleted, along with Carlos's morale.txt file.

Community solutions

Emanuele Picariello