HTB OnlyHacks Walkthrough
The box “OnlyHacks” is a web based box having a Insecure Direct Object Reference (IDOR) vulnerability. It is rated Very Easy on HTB
I started up the target and connected to the HTB VPN. I then, opened up a new tab and pasted in the provided URI.
A web application opened up with a login page along with a signup prompt. I checked the source for any commented-out credentials or any secrets at all — did not find any, so moved to the /register endpoint.
In the register page we are asked for a lot of info like username, password, profile picture, email, age, bio and our preference.
I filled up the profile with expected data to analyze the application behaviour first.
After registering a new account, cards of different profiles show up.
Upon source code inspection, it turns out to be static cards instead of dynamically generated. I then, tried for common endpoints like sitemap.xml, robots.txt, security.txt — no luck.
So I decided to run a fuzzer to check if any common endpoints are available. The results did not reveal any unknown endpoints. I decided to change my approach and analyze the application behaviour further.
After liking all the profiles, a match appears in /chat endpoint. On opening the chat, I saw a parameter “rid=6”
The rid is being used to open particular chats.
I tried with a few other rid values, since it was a integer and likely incremental and
for the rid value of 3, found out the flag.
Submitted the flag and pwned the room successfully.
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The primary vulnerability here was that the application was not checking whether the user has proper authorization to view a particular rid/chat.
To prevent this, we have to implement proper access controls and authorization checks at the backend. We should also preferrably use UUID/GUID identifiers for reference chats instead of incremental integer UID which can be easily guessed or predicted.
