WhatsApp currently requires iOS 15.1 or higher.
The most significant danger of downloading an IPA from unofficial sources is security. WhatsApp is a primary vector for personal communication—messages, photos, videos, contacts, and even payment details in some regions. An IPA file obtained from a forum, file-sharing site, or a "tweak store" can be modified to include spyware, keyloggers, or ransomware. Since iOS 9.3.5 has not received a security update since 2018 (aside from the rare critical patch like the Pegasus exploit fix), any sideloaded app would operate on a deeply vulnerable operating system. In other words, by seeking a working WhatsApp IPA, a user might be handing over the keys to their entire digital life to an unknown third party. whatsapp ipa for ios 9.3.5 download