Jeffrey Goldberg, editor-in-chief of The Atlantic, inadvertently learnt specifics about US plans for attacks on Houthi targets after he was added to a group chat on the popular messaging app Signal Messenger.
Mr Goldberg says he was mistakenly included in the chat "Houthi PC small group" within the Signal app, which often promotes its independent status and emphasises its encryption and security features.
"On Tuesday, March 11, I received a connection request on Signal from a user identified as [US National Security Adviser] Michael Waltz," Mr Goldberg wrote in a Monday article detailing the inadvertent leak.
Several users were involved in the group, including one identified as "JD Vance", presumably the Vice President.
The large-scale military strikes against the Iran-backed Houthis were in response to the group's continued attacks on Red Sea shipping. At least 53 people, including five children, were killed and 98 others injured in the first round of strikes on March 15, according to a Houthi Health Ministry spokesman.
A White House National Security Council representative said that the Signal chat appears to be authentic and that officials are reviewing how an "inadvertent number" was added to the chain, ABC reported.
"The thread is a demonstration of the deep and thoughtful policy co-ordination between senior officials," the representative said. "The ongoing success of the Houthi operation demonstrates that there were no threats to our servicemembers or our national security.”
US President Donald Trump told reporters he was unaware of the incident, and then criticised The Atlantic.
"I think it's not much of a magazine but I know nothing about it ... well, it couldn't have been very effective because the attack was very effective. I can tell you that I don't know anything about it. You're telling me about it for the first time."
Senator Jacky Rosen, a Democrat member of the Senate armed services committee and committee on foreign relations, said the Trump administration’s "reckless handling of highly sensitive information regarding US military operations is an inexcusable failure".
"Using an unclassified communications platform to discuss classified military operations and being careless enough to add someone without the proper clearance is a dangerous level of incompetence," Ms Rosen said.
Signal's founder, Moxie Marlinspike, poked fun at the very serious development.
"There are so many great reasons to be on Signal. Now including the opportunity for the vice president of the United States of America to randomly add you to a group chat for co-ordination of sensitive military operations," he posted on X. Don’t sleep on this opportunity."
Although not as popular as WhatsApp or conventional text messaging, Signal has a fiercely loyal user base, which includes journalists and government officials looking to maintain security.
According to Signal's website, the text-based communication app made its debut in 2012.
"Signal is a non-profit with no advertisers or investors, sustained only by the people who use and value it," reads the company's biography. It is "protecting free expression and enabling secure global communication through open-source privacy technology".
Mr Marlinspike, from California, describes himself as a founder, engineer, sailor, captain and shipwright.
"I hope to contribute to a world where we value skills and relationships over careers and money, where we know better than to trust cops or politicians, and where we're passionate about building and creating things in a self-motivated and self-directed way," Mr Marlinspike's biography on his website reads.
Signal has gained popularity as it pushed the idea of a messaging platform that had no advertisements, no data trackers and no affiliate marketing. It is free, and describes itself at an independent non-profit "not tied to any major technology companies … supported by grants and donations from people like you".
In 2018, Signal established the Signal Foundation to support the platform's values and growth, all while helping to "investigate the future of private communication".
The independent and privacy-focused origins of Signal were bolstered further that same year when WhatsApp co-founder Brian Acton joined the Signal Foundation with a major donation.
In a post on X last week, Signal quotes its president Meredith Whittaker as saying: "We have ceded so many of the core operations of our lives and institutions to tech, we must recognise that strong encryption isn’t the enemy of security – it *is* security."
According to TechCrunch, Signal had about 20 million active monthly users as of 2020. Other estimates indicate that it may have between 40 million and 70 million as of 2025.
For all the promotion of encryption, privacy and a lack of data trackers, however, the recent incident involving US military operations in Yemen prove that the app is only as secure as the people using it.
