OkHttp before 2.7.4 and 3.x before 3.1.2 allows man-in-the-middle attackers to bypass certificate pinning by sending a certificate chain with a certificate from a non-pinned trusted CA and the pinned certificate.
https://publicobject.com/2016/02/11/okhttp-certificate-pinning-vulnerability/
https://koz.io/pinning-cve-2016-2402/