Hi There,

Renganathan here.

This write-up is about an accidental bug that I found on LinkedIn.

So that was the early time when I joined LinkedIn and I didn’t know much about the working functionalities. I’ve used only Instagram in my life *_*

I was trying to send a connection request to a person and I noticed I can give a personalized note with the requests. I added a message with around 650 characters approximately.

But LinkedIn allows, only 300 characters. So As a noob, what I did was, I used inspect element to change the maxlength=300 value. And then I sent the request.

BOOM!

It didn’t work, what else did you expect :/

Then I thought of using Burp Suite to add more content, which is more than 300 characters in the POST request. Something like below

“message”:{“values”:[{“value”:”follow me on Instagram”}]}

And I clicked forward, and the connection request was sent successfully. Then I went to mynetwork/invitation-manager/sent/ to see the sent connection requests.

BOOM!

This worked :)

So, the characters I sent were more than 300 obviously and it was sent successfully.

So, Reporting this as a business logic error won’t be good. So I tried adding a very huge request to my test account with a kind of hundred thousand characters.

I opened it from my android phone and the app was crashed.

I was like “IS THIS A DOS? VULNERABILITY”

TimeLine:

Oct 10, 2020- Reported

Oct 14, 2020- Triaged

Dec 20, 2020- Retested

Dec 22, 2020- Patched & Acknoweldgedment received

Thanks for reading :)
Stay Safe.

https://www.instagram.com/renganathanofficial/

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