While both Alipay and WeChat have acknowledged the issue, it's unclear how many users have been affected. But with around 1.5 billion users between the two, quite a few people could be at risk. The problem appears to arise when users link their Apple ID to their payment method, though there's no word on how the Apple IDs were stolen or by whom.

An Apple spokesperson pointed the Wall Street Journal to its page on how to secure Apple IDs. Instructions include a strong password, hard to guess answers to security questions and two-factor authentication.