Document Title: =============== Flowdock API Bug Bounty #4 - Persistent RSS Vulnerability References (Source): ==================== http://www.vulnerability-lab.com/get_content.php?id=1575 Vulnerability Magazine: http://magazine.vulnerability-db.com/?q=articles/2015/09/29/flowdock-api-four-vulnerabilities-patched-batch Release Date: ============= 2015-09-27 Vulnerability Laboratory ID (VL-ID): ==================================== 1575 Common Vulnerability Scoring System: ==================================== 3.9 Product & Service Introduction: =============================== Chat & inbox for teams.. One place to talk and stay up-to-date. Flowdock is a team collaboration app for desktop, mobile & web. Work on things that matter, be transparent and solve problems across tools, teams & time zones. Try it for free for 30 days. Keeping Flowdock`s environment and customer data safe and secure is a top priority for us. Find more details on our Help pages. Don`t hesitate to contact us at support@flowdock.com should you have any questions about Flowdock`s security. (Copy of the Vendor Homepage: https://www.flowdock.com/security ) Abstract Advisory Information: ============================== The Vulnerability Laboratory Research Team discovered an application-side input validation exception-handling web vulnerability in the official Flowdock online service web-application. Vulnerability Disclosure Timeline: ================================== 2015-08-17: Researcher Notification & Coordination (Benjamin Kunz Mejri) 2015-08-18: Vendor Notification (Flowdock Security Team - Bug Bounty Program) 2015-08-18: Vendor Response/Feedback (Flowdock Security Team - Bug Bounty Program) 2015-08-19: Vendor Fix/Patch (Flowdock Developer Team) 2015-09-28: Public Disclosure (Vulnerability Laboratory) Discovery Status: ================= Published Affected Product(s): ==================== Rally Software Product: Flowdock - Online Service (Web-Application) [API] 2015 Q3 Exploitation Technique: ======================= Remote Severity Level: =============== Low Technical Details & Description: ================================ An application-side input validation web vulnerability has been discovered in the official Flowdock online-service web-application. The vulnerability allows remote attackers to inject own malicious script codes on the application-side of the vulnerable context function or service module. The vulnerability is located in the rss feed url input field of the Rss Connector module POST/GET method request. Remote attackers with low privilege application user accounts are able to inject own malicious script codes on the application-side of the service. The request method to inject malicious context is POST & GET and the attack vector is located on the application-side and client-side of the flowdock api web-service. Remote attackers are able to inject malicious script codes on the application-side to compromise flowdock auth api path by session manipulation or session evasion attacks. The attacker injects via rss url website input malicious payloads which demonstrates the injection point and the execution point is in the preview error message in the rss connector context module. The exception-handling of the preview handles the input with wrong encoding which results in a direct execution of script code after the first injection procedure took place. The firewall does not prevent the loading of external websites because only script tags are blocked. By loading iframes or img src with svg tags the filter can be bypassed. The security risk of the persistent input validation web vulnerability is estimated as medium with a cvss (common vulnerability scoring system) count of 3.8. Exploitation of the persistent input validation web vulnerability requires a low privilege web-application user account and low user interaction. Successful exploitation of the vulnerability results in session hijacking, persistent phishing attacks, persistent redirect to external sources and persistent manipulation of affected or connected service module context. Request Method(s): [+] POST Vulnerable Module(s): [+] RSS Connector (flowdock.com/jari/auth/rss?) Vulnerable Function(s): [+] Feed Preview Vulnerable Parameter(s): [+] preview > preview-error Proof of Concept (PoC): ======================= The security vulnerability can be exploited by remote attackers with low privilege application user account and low user interaction. For security demonstration or to reproduce the security vulnerability follow the provided information and steps below to continue. Manual steps to reproduce the vulnerability ... 1. Login to your account at the flowdock website 2. Surf to the main dashboard module 3. Create a new organization Note: A new menu opens in a popup 4. Click in the Inbox Sources category the Rss module 5. Inject a script code payload without