The Federal Trade Commission issued strong warnings to celebrities and influencers who peddle products on social media in exchange for cash.

The FTC warned celebrities that they must disclose the compensation they receive in return for peddling products on social media such as Instagram or Twitter.com.

According to The Consumerist, the FTC issued warning letters on Friday, April 21, to 90 social media influencers and the brands that pay them to peddle their products.

The report did not disclose who the FTC sent the letters to, but the FTC did provide a template of the letter.

The letters included multiple warnings and reminders about disclosing endorsements to their followers.

“Consumers should be able to notice the disclosure easily, and not have to look for it,” the letter states.

“For example, consumers viewing posts in their Instagram streams on mobile devices typically see only the first three lines of a longer post unless they click ‘more,’ and many consumers may not click ‘more.’ Therefore, you should disclose any material connection above the ‘more’ button.”

“It is often unclear whether an Instagram user is paid to post a product endorsement or if they genuinely use it,” said Kristen Strader, who started a petition to bring the FTC’s attention to the stars’ failure to disclose their relationship with brands.

The Campaign for a Commercial-Free Childhood also issued a statement:

“We’re glad the FTC is encouraging influencers on Instagram to be more forthright, but we hope they expand that initiative to include YouTube and other social media, which reach millions of children and we hope the FTC will take strong action against any influencers who refuse to comply with the rules.”