As for the Bitmart app on the Google Play Store,, it's now updated to the latest version, and it's always best to download apps from trusted official stores like Google Play or the App Store. I would also advise the OP not to download it from external links, as there’s a real risk of ending up with a fake app or one that contains a Trojan or even clicking on a phishing domain imitating the original exchange.
Downloading mobile apps from third party sources often carries big risks. Especially Apps (exchanges, financial services, payment services, wallets) should be downloaded exclusively from the store or official website, otherwise they may contain phishing malware.
Most exchanges provide a direct download link from the exchange's official website or a link to Google Play or the App Store via QR scanning. Therefore, should only download apps from official links.