WhatsApp has rolled out a new security measure that prevents users from logging in to the app if their devices run an outdated operating system, on both Android and iOS. Affected users are shown the steps needed to update their devices so they can keep using the service.

The measure does not require installing a new version of the app. Instead, it directs users to their device settings to install the latest available operating system update. WhatsApp has not yet published a list of the versions whose users will be blocked from logging in.

The step is intended to strengthen user security, since devices running old operating systems may be exploited through security vulnerabilities, potentially allowing attackers to install malware and access the data stored on them.

WhatsApp has begun introducing the feature gradually to selected Android and iOS accounts through a server-side update, without the need for a new app release.