If WhatsApp has suddenly put a screen in front of you asking for a system update, your phone’s software is the problem, not the app. WhatsApp has started blocking logins on Android phones and iPhones running old operating system versions, and there is no skip button. The report comes from WABetaInfo, and it was spotted on both platforms over the weekend.

Updating WhatsApp Itself Will Not Clear It
This one is switched on from WhatsApp’s side, not through an app update, so you can be on the newest WhatsApp from the store and still hit the screen. What the screen asks for is the phone’s own software. Go into Settings, install whatever system update is waiting, then come back and log in. It also shows you where to check your current version, in case you have no idea what your phone is running, which most people don’t.
Only Some Accounts Are Getting It So Far
WhatsApp is switching this on for selected users rather than everyone at once, and it has not said which Android or iOS versions trip it. So two people on the same WhatsApp build can have completely different experiences depending on the phone underneath. For reference, the official floor right now is Android 6.0 and iOS 15.1, and the iPhone minimum moves up to iOS 15.5 on November 30. Whether the new check uses those exact lines or something stricter, WhatsApp is keeping to itself.
Why WhatsApp Is Doing This
Security, and not in the vague sense. An old operating system has known holes that attackers already know how to use, and end to end encryption does nothing for you if the phone itself is compromised before the message is even sent. A link from someone you trust is still a link, and if their phone was infected through an old Android build, the encryption carried it to you perfectly intact. WhatsApp is treating the phone’s software as part of its own security wall now.
One thing it is not: the separate warning WhatsApp is testing for unofficial WhatsApp Web clients. That targets fake apps, not old phones, and it’s easy to mix the two up since both landed the same week.
If Your Phone Can’t Update Any Further
That’s the unanswered part. WhatsApp has not said what happens to a phone that simply has no newer system version to install, and for an old enough handset the only route left may be a different phone.