The vulnerabilities, discovered by Citizen Lab and Lookout, were known as the "Trident":
The study of iOS 9.3.5 and its IPA architecture highlights the tension between security and preservation. The OS sits on the precipice of the 32-bit/64-bit divide. Unlike newer iOS versions which utilize hardened runtime protections and encrypted IPAs that are difficult to analyze, iOS 9.3.5 IPAs are relatively accessible for reverse engineering. ios 9.3.5 ipa