U.K. government websites and more than 4,000 others worldwide have reportedly been exploited by malware that harnesses visitors’ computers to mine cryptocurrency.

According to BBC, the incident was first revealed after British security researcher Scott Helme, who raised the alarm that users browsing the website of the U.K. Information Commissioner’s Office (ICO) are affected by the malware, dubbed Coinhive, which illicitly mines the anonymous cryptocurrency Monero.

The ICO subsequently closed its website when the issue was revealed, the report indicates. At press time, the site was still down, citing “maintenance.”

The BBC said the malware spread after having compromised a website plug-in service named Browsealoud, which is used to help blind or partially sighted users access website content.

According to the report, the maker of the plug-in, Texthelp, confirmed that its product was breached for four hours by the mining malware. Helme said the malware had now been disabled.

In addition to the ICO website, the report said other British sites are also affected, including the Student Loans Company and Barnsley Hospital, as well as thousands of others worldwide.

According to another report from Australian news source ABC.net, several government sites in Queensland, as well as the Victorian Parliament, also appeared to have been affected.

According to a November 2017 report, Coinhive has become the sixth most common form of malware. It has previously been discovered in Google ads, the Ultimate Fighting Championship website and TV network Showtime, among many others.

Hacker image via Shutterstock