It's been about a month since users discovered that popular torrent site The Pirate Bay had a hidden in-browser cryptocurrency miner on its pages that surreptitiously utilized visitors’ CPUs to mine Monero.

Finding a secret cryptocurrency miner on a torrent site didn’t take a lot of people by surprise, but they've started appearing in more reputable websites since then, including those run by CBS-owned cable network Showtime, and, most recently, the Pulitzer Prize-winning fact-checking website PolitiFact.

As with the other two cases, the Javascript-based miner on PolitiFact was provided by third-party service CoinHive. The company, which takes a 30 percent cut of the mined Monero, says its product is a legitimate way for websites to make money and doesn’t endorse anyone using its code without first informing visitors.

When asked last month about the miner on its website, Showtime declined to comment on the matter and wouldn't say if it had been hacked. PolitiFact has been more forthcoming, explaining that it has now removed the code and is currently investigating how it got there.

The practice of using these miners is increasing at an alarming rate. A recent report by ad blocker company AdGuard reveals that, less than one month since CoinHive was launched, 220 of the top 100,000 websites are running it or some other Javascript-based miner. That may not sound like a lot, but they have an aggregated audience of over 500 million people. It is noted, however, that most of these are from the “gray zone” of pirate TV and video sites, torrent trackers, and pornographic websites.