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From:Vulnerability Lab <research_(at)>
Subject:Grindr v2.1.1 iOS & Account System - Breach Attack Vulnerability

Document Title:
Grindr v2.1.1 iOS & Account System - Breach Attack Vulnerability

References (Source):

Release Date:

Vulnerability Laboratory ID (VL-ID):

Common Vulnerability Scoring System:

Product & Service Introduction:
Grindr, which first launched in 2009, has exploded into the largest and most popular all-male location-based social network out there.
With more than 5 million guys in 192 countries around the world -- and approximately 10,000 more new users downloading the app
every day -- you’ll always find a new date, buddy, or friend on Grindr. Grindr is a simple app that uses your mobile device’s
location-based services to show you the guys closest to you who are also on Grindr. How much of your info they see is
entirely your call.

(Copy of the Vendor Homepage: )

Abstract Advisory Information:
The Vulnerability Laboratory Research Team discovered the well known Breach Attack issue in the official Grindr v2.1.1 iOS mobile application and connected account system.

Vulnerability Disclosure Timeline:
2015-01-23: Researcher Notification & Coordination (Benjamin Kunz Mejri - Evolution Security)
2015-01-23: Vendor Notification (Grinder - Bug Bounty Program)
2015-02-12: Vendor Response/Feedback (Grinder - Bug Bounty Program)
2015-04-01: Vendor Fix/Patch (Grindr Developer Team - Reward: x  & Manager: x)
2015-05-04: Public Disclosure (Vulnerability Laboratory)

Discovery Status:

Exploitation Technique:

Severity Level:

Technical Details & Description:
The grindr v2.1.1 & connected account system is vulnerable to the famous `breach attack`. Remote and local attackers can leverage data leaked by compression to recover targeted sections of the plain-text, inject partial plain-text into application-side or client-side victim requests or aeasure the data size of encrypted traffic of the mobile application and connected account system. The following conditions must match to become a target of the issue ...

- Become served from a server that uses HTTP-level compression
- Reflection of user-inputs in HTTP responses (context body)
- Reflect a secret data  (token, csrf-x) in HTTP response bodies

The vulnerability affects the ./user module of the server online-service. The following issues are matching to grant the successful exploitation ...

- We verified that the page content is served via HTTPS protocol
- We verified that the server is using the HTTP-level compression
- We verified that URL encoded GET input locale was reflected into the HTTP response context body
- We verified that the HTTP response contains in the body a secret token named authenticity_token that is already known as broken of the reports due to the pentest

Proof of Concept (PoC):
--- PoC Session Logs ---
POST /users?locale=en_997546 HTTP/1.1
Content-Length: 235
Content-Type: application/x-www-form-urlencoded
Cookie: _primus-
Connection: Keep-alive
Accept-Encoding: gzip,deflate
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/28.0.1500.63 Safari/537.36
Accept: */*

HTTP/1.1 200 OK
Cache-Control: max-age=0, private, must-revalidate
Content-Type: text/html; charset=utf-8
Date: Fri, 23 Jan 2015 19:23:31 GMT
ETag: "7d2e9f335d5d83fea93c15bcb81eea84"
Server: nginx/1.2.3 + Phusion Passenger 3.0.17 (mod_rails/mod_rack)
Status: 200
X-Powered-By: Phusion Passenger (mod_rails/mod_rack) 3.0.17
X-Rack-Cache: invalidate, pass
X-Request-Id: 89fc8be001a8329aec428209c08529ab
X-Runtime: 0.175325
X-UA-Compatible: IE=Edge,chrome=1
Content-Length: 4425
Connection: keep-alive
Original-Content-Encoding: gzip


Solution - Fix & Patch:
Disabling the HTTP protocol compression
Separating secrets from user input in the application
Randomizing of secrets in separate request
Masking of secrets (XORing)
Protecting the vulnerable pages with CSRF issues by usage of a secure token
Length hiding by adding own random numbers of bytes to the responses itself
Rate-limiting the requests to prevent

Security Risk:
The security risk of the Breach Attack issue in the iOS application that is connected to the account system is estimated as high. (CVSS 6.7)

Credits & Authors:
Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ([email protected]) []

Disclaimer & Information:
The information provided in this advisory is provided as it is without any warranty. Vulnerability Lab disclaims all warranties, either expressed
or implied, including the warranties of merchantability and capability for a particular purpose. Vulnerability-Lab or its suppliers are not liable
in any case of damage, including direct, indirect, incidental, consequential loss of business profits or special damages, even if Vulnerability-Lab
or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for
consequential or incidental damages so the foregoing limitation may not apply. We do not approve or encourage anybody to break any vendor licenses,
policies, deface websites, hack into databases or trade with fraud/stolen material.

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