TL;DR: Uber was vulnerable to subdomain takeover on saostatic.uber.com via Amazon CloudFront CDN. Moreover, Uber’s recently deployed Single Sign-On (SSO) system at auth.uber.com, which is based on shared cookies between all *.uber.com subdomains, was found vulnerable to session cookie theft by any compromised *.uber.com subdomain. Therefore, the impact of the subdomain takeover could be increased to Authentication Bypass of Uber’s full SSO system, yielding access to all *.uber.com subdomains protected by it (e.g. vault.uber.com, partners.uber.com, riders.uber.com, etc). Uber resolved the subdomain takeover vulnerability and granted a $5.000 bounty for the two combined issues.
TL;DR: Login CSRF in combination with an HTTP Referer header-based open redirect in Airbnb’s OAuth login flow, could be abused to steal OAuth access tokens of all Airbnb identity providers and eventually authenticate as the victim on Airbnb’s website and mobile application. This attack did not rely on a specific OAuth identity provider app configuration flaw (e.g. wildcards in whitelisted redirect_uri URLs), which made it generic for all Airbnb’s identity providers (Facebook & Google at the time of reporting). Airbnb fixed both the login CSRF and open redirect issues and awarded a $5.000 bounty back in the summer of 2016.
I publicly disclosed a vulnerability that I responsibly disclosed to Ubiquity via the HackerOne platform. It concerned a subdomain takeover issue via Amazon Cloudfront (ping.ubnt.com) in combination with shared session cookies between subdomains on *.ubnt.com, which ultimately lead to a complete Authentication Bypass of their SSO system (sso.ubnt.com). It can be found here.