Signed up for Klaviyo? Dozens of advertisers may have seen your password

Newly revealed security research found that until recently, marketing tech giant Klaviyo was inadvertently sharing the sign-up information of its new customers, including their passwords, with outside advertisers.

Sam Jadali, a security researcher and co-founder of cybersecurity startup Melurna, told TechCrunch that the web form on Klaviyo’s sign-up page was misconfigured between at least February 2024 through November 2025, though likely longer.