Vimeo Livestream Bug Bounty WriteUp

Mohamed Slamat
Jan 29 · 3 min read

Phishing Using Signup at Livestream API

Hi guys , Today I will share with you Writeup about this vulnerability

So to signup up in Livestream, we need to send email,full_name,password to the API endpoint

Payload :

curl -i -X POST -d ‘’

API Response :


And a mail contain URL activation will send to this mail :

As you see a message start with Hi Full_name …..

But if we send the same payload again with same user

API Response :

{“name”:”DuplicateEntryError”,”message”:”email already exists.”,”field”:”email”}

Since the user already exist, We can’t register him again and he will receive nothing , Nah ?

So after guessing the backend code …

I think is written by this way :

Pseudo code :

if email in db : 
response = "email already exists"
else :

I noticed that email is not an email format , I mean you can send what u want as email some blabla and the account will opened !

To login with this account , you just need to inspect element and change the type of input email to text !

So our blabla will store in database two !

Hmmmmmm !!!

Okey let’s meet mail() function in PHP

How it work ?


Let’s talk about $email variable :

The mail() function can send to one or more emails !!! , If the $email variable contain many emails splited by the COMMA “,”

So if the $email = “,”; a mail will send to the both of emails with same subject & message 😮

And since we control the full_name in our payload …

And we can pass if email in db because :

“,” != “

Let’s Phish 😊 ✌️ :

curl -i -X POST -d ‘email=blabla, noticed that your account is Hacked by someone , Please confirm and reset your account here

A mail was sent to an existent user ( using livestream api

PS : Im not sure that the api use mail() function or even they coded by php But it worked xD ✌️

Impact :

Since there is a small IDOR in the api

ie :

Attacker can get users info from accounts/id and using some OSINT , he will get Livestream users emails

Attacker can send unlimited phishing mails to Livestream users !

Livestream Response :

i) This is not a security Bug ! => Report Closed !

ii ) Me: Ah really, are you sure ? Livestream: Wait … This is a Security bug => Report Opened => Report Triaged

iii) Livestream send a Bounty ( Not full )

IV ) Livestream closed report as #Duplicated with another report based on XSS (I can’t talk about it for program confidentiality ) which have no relation with Phishing and bypassing signup mail func xD …

I hope you enjoyed, Happy Hunting

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