The malicious link will install cookies on the victim's smartphone, or download a browser extension which can be used to serve more adverts to them – generating revenue for the cybercriminals behind the text messages, according to security researchers.
Whats App was recently praised by Amnesty International, which dubbed the Facebook-owned instant messenger as the "most secure" platform available to consumers.
Whats App is the most popular messaging app on the planet, with a staggering one billion people using the chat app.
Worse still, these messages are coming from trusted contacts, who are being encouraged to send the fake vouchers to as many people as possible.
The scam was spotted by Action Fraud, which says it’s aware of fake vouchers claiming to be from Asda, Topshop, Sainsbury’s, Marks & Spencer, Tesco, Asda, Nike, Lidl, Aldi and Singapore Airlines.
However the recipient name is actually fake and is designed to trick Whats App users into trusting the web address for the alleged £100 Sainsbury's voucher.
The messages reads: "Hey have you heard about this? "They are expanding their store network and they launched this promotion. I got mine already." (Although the URL listed in the text appears to direct users to Sainsbury's website, it is a scam webpage designed to trick Whats App users into handing over personal information.
A fake Asda voucher message seen by the displays the message, “Hello, ASDA is giving away £250 Free Voucher to celebrate 68th anniversary, go here to get it,” alongside a cleverly formulated url that you should not click.