Online advertising firm Adform suffered a supply-chain attack that delivered cryptocurrency-stealing scripts to websites using its ad platform, replacing wallet addresses copied to visitors’ clipboards with ones controlled by an attacker.

Adform is one of Europe’s largest adtech firms, providing a full-stack platform that includes Demand-Side Platform (DSP), Supply-Side Platform (SSP), ad servers, and management tools.

Security researcher Kevin Beaumont discovered the malicious activity, saying that it stemmed from ‘trackpoint-async.js,’ Adform’s JavaScript tracking script served from ‘s2.adform.net’ and embedded in every website using the advertising platform.

According to the researcher, the trojanized JavaScript continuously monitors the clipboard of users visiting websites that embed trackpoint-async.js.

If the script detected Bitcoin, Ethereum, or TRON wallet addresses, it replaced them with an attacker-controlled address to redirect cryptocurrency payments.