WhatsApp users accessing the service via an unauthorised app are being locked out of the messaging service for 24 hours.
WhatsApp Plus provides ways to customise the appearance of WhatsApp conversations and to increase the size limit of attached video and sound files. It also has a tool to prevent others seeing when users last logged in.
In a post on the WhatsApp website, the company said WhatsApp Plus is not authorised or supported by the company.
It also stated that it contains source code that it can’t guarantee as safe, with private information “potentially being passed to third parties without your knowledge or authorisation”.
In order to access WhatsApp again users must uninstall WhatsApp Plus and download the official version of WhatsApp. Users will then be able to access WhatsApp after a “24 hour countdown”.
A moderator of the development community supporting WhatsApp Plus said in a Google+ post that it had received “a cease and desist letter” from WhatsApp obligating it to “remove all download links and unfortunately delete this community”.
In a separate announcement, WhatsApp introduced a web-based version of the messaging service, on which users can continue conversations they have on their phones in a desktop computer browser.
To access the web version, users must go to the relevant page on WhatsApp’s website and scan a QR code to pair their phone account with the browser version.
It is currently only available for users of the Google Chrome browser with Apple “platform limitations” meaning it is not possible to provide the service to iOS users, according to WhatsApp.
WhatsApp recently revealed it has 700 million monthly active users, with an average of 30 billion messages sent per day.