Last week, Mashable reported that on X (formerly Twitter), users were noticing a new type of advertisement: Minus a regular handle or username, the ad’s headline looks like a normal tweet, with the avatar a miniature of whatever featured image appears in the body of the post. There is no notification in the upper right-hand corner saying “Ad,” and users can’t click on the ad to see more about who paid for it.

“Dude what the fuck is this I can’t click on it there’s no account name there’s no username I’m screaming what the hell it’s not even an ad,” one user tweeted. But Twitter’s new ad interface may be more than just annoying—it may be illegal.

Under Section 5(a) of the US Federal Trade Commission Act, companies are banned from using deceptive ad practices, meaning consumers must know that ads are, well, ads. For social platforms, this means that any native advertising, or advertising designed to look like content on the platform, needs to be clearly labeled.

“There’s really no doubt to us that X’s lack of disclosure here misleads consumers,” says Sarah Kay Wiley, policy and partnerships director at Check My Ads, an ad industry watchdog group. “Consumers are simply not able to differentiate what is content and what is not paid content. Even I’ve been duped, and I work in this space.”

X did not immediately respond to a request for comment.

X has two feeds, a Following feed that is meant to show users content from accounts they follow and a For You feed that includes algorithmically recommended content from across the platform. Wiley says she has seen examples of this unlabeled ad content in both feeds. What’s more confusing is the fact that some other content is still labeled as ads. “It’s really egregious because some ads are still marked as ads,” says Wiley. “It really provides opportunities for fraudulent marketers to reach consumers.”

An FTC staff attorney with the agency’s ad practices division, who spoke to WIRED on condition of anonymity, says that the agency encourages platforms to use a consistent format for advertising disclosures in order to avoid confusing customers.

And Wiley says that if advertisers think X is doing the work of labeling their content when it’s not, they could also face compliance issues for not properly disclosing that their posts are ads. “The advertisers themselves are also victims,” she says.