"The original article – now amended and associated with the conclusions of this review – led to follow-up coverage, some of which sustained the wrong impression given at the outset. The most serious inaccuracy was a claim that WhatsApp had a “backdoor”, an intentional, secret way for third parties to read supposedly private messages. This claim was withdrawn within eight hours of initial publication online, but withdrawn incompletely. The story retained material predicated on the existence of a backdoor, including strongly expressed concerns about threats to freedom, betrayal of trust and benefits for governments which surveil. In effect, having dialled back the cause for alarm, the Guardian failed to dial back expressions of alarm."

From this linked article.