Breaking Appointments and Job Interview Schedules With Malformed Times

Facebook recently added an “Appointments” feature to pages. After a bit of searching through all the requests made I found that it was possible to use malformed times to break the appointment tab. The impact of this is that a malicious admin/editor can create irreversible damage to Appointments and Job Interview Schedules. This will stay permanently so even if the malicious actor was removed from the page. This could be especially impactful in a large organizations Facebook page as they would need to remake the entire page losing all current following on it to get a working Appointments tab back.

Proof of Concept

1) Go to https://www.facebook.com/PAGEID/manage_jobs

2) Click on a job application and hit schedule interview

3) Turn on a HTTP Interceptor such as burp suite

4) Intercept the graphql query and change suggested_end_time to a malformed time such as 15393834250000

5) The Appointments calendar should now be broken and if anybody trys to view the applicants schedule info the window will break on them

Video

Timeline

Submitted- October 19th, 2018

Triaged- October 24th, 2018

Bounty Awarded($500)- November 13th, 2018