Original Writeup on finnersio’s blog

We are first presented with what looks like a store page to buy merchandise:

The only interactive portion of the site is the merch request form, that sends a POST request.

We can view that using either a MITM Proxy or just the Network Tab.

When submitting the default request, it replies with an error: You must be a member to request free merch

Looking at the POST has the following payload:

-----------------------------429214736125992314531083334719
Content-Disposition: form-data; name="name"

a
-----------------------------429214736125992314531083334719
Content-Disposition: form-data; name="email"

a@a.a
-----------------------------429214736125992314531083334719
Content-Disposition: form-data; name="address"

a
-----------------------------429214736125992314531083334719
Content-Disposition: form-data; name="role"

viewer
-----------------------------429214736125992314531083334719--

There is a role attribute to the form. Changing this to member and sending the request should reveal the flag.

The server responds with: Congratulations! Not only do you get a free Hoodie, you also get a flag: SECEDU{yes_yes_yes_we_want_free_merch}

Flag: SECEDU{yes_yes_yes_we_want_free_merch}