Grindr v2.1.1 iOS Bounty #1 - (Session) Auth Bypass Vulnerabilities

Type securityvulns
Reporter Securityvulns
Modified 2015-05-04T00:00:00


Document Title:

Grindr v2.1.1 iOS Bounty #1 - (Session) Auth Bypass Vulnerabilities

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 a redirect vulnerability and a token auth bypass issue in the official Grindr v.2.1.1 iOS mobile web-application.

Vulnerability Disclosure Timeline:

2015-01-22: Researcher Notification & Coordination (Benjamin Kunz Mejri - Evolution Security) 2015-01-22: Vendor Notification (Grinder - Bug Bounty Program) 2015-02-04: 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:


Affected Product(s):

Grindr LLC Product: Grinder - iOS Mobile Web Application (API) 2.2.1

Exploitation Technique:


Severity Level:


Technical Details & Description:

Multiple web vulnerabilities has been discovered in the official Grindr v2.1.1 iOS mobile web-application.

1.1 The first issue is that due to the password change the app is allowed to request through the browser the service. Attacker with a privileged account can request via POST and intercept the request to get a valid token. After the token has been saved the attacker is able to change the email value. After changing the email value the attacker is able to get access to another users/administrator account. To exploit the bug the session needs to be tampered, the request needs to be intercepted, stoped to store the valid token. After the token is stored the attacker can use an mobile application tamper to inject the new email value. The fail was that the token is not connected to the session itself but the request requires only a valid token. In the password change module were the same problem occurs is no token available in the request that send you through the iOS safari browser to the account system.

Vulnerable Application(s): [+] iOS

Vulnerable Module(s): [+] Email Change [+] Password Change

Vulnerable Parameter(s): [+] emailChange%3FauthenticationToken [+] password?email=

1.2 The second issue is located in the file location but in the redirect_url parameter. Remote attackers can inject external sources to redirect a victim through the application to another malicious external source. The bug is in the same location which allows remote attackers or local privileged user accounts to exploit the vulnerability in combination with the token and email issue above.

Vulnerable Module(s): [+] success

Vulnerable Parameter(s): [+] redirect_url

Proof of Concept (PoC):

1.1 The session token reset auth bypass issue can be exploited by local low privileged user accounts without user interaction.

Email Change PoC:

Password Change PoC: NO TOKEN REQUIRED!!!!

1.2 The redirect web vulnerability that is exploitable in the success module can be exploited remote accounts without low or medium user interaction.


Solution - Fix & Patch:

1.1 The token vulnerability can be patched by a secure implementation that disallows to review or to capture the session information. A valid token is not allowed to reset other account and needs to be connected to the session id information and co. to prevent an account system compromise.

1.2 The redirect web vulnerability cna be patched by a secure parse and encode of the vulnerable redirect_url value in the success module. Restrict the request and disallow external source to prevent exploitation.

Security Risk:

1.1 The security risk of the token issue in the reset and change function is estimated as critical

1.2 The security risk of the redirect web vulnerability in the account system success is estimated as medium. The issue can be combined with the token vulnerability to compromise the account system.

Credits & Authors:

Vulnerability Laboratory [Research Team] - Benjamin Kunz Mejri ( []

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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