Initially, Chrome Web Store allows for the extension of virtual currency miners with certain conditions. One of them, the extension only serves to mine cryptocurrency.
Another requirement is that users who use the extension know that the extension serves to mine the virtual currency.
Warning users is important because the process of mining virtual currency will usually force the computer to work very hard.
"Unfortunately, 90 percent of extensions with miner codes that developers try to upload to Chrome Web Store do not meet these requirements, so the miner's extensions have been denied for inclusion or removal from the Store," said James Wagner, Extensions Platform Product Manager, Google in a blog post.
In December, Google had to remove the Archive Poster extension after Bleeping Computer reported that the Tumblr extension actually mine Monero currency on more than 105 thousand devices.
Some other extensions, which sometimes disguise themselves as URL shorteners, are also deleted by Google within the past six months.
Virtual currencies like Bitcoin or Ethereum can be obtained by "mining" when miners use computers to authenticate and record transactions.
This process is very draining computer power. Therefore, fraudsters try to use other people's devices to earn virtual currency without having to make an adequate computer.
The scheme is called "cryptojacking". Google says they no longer accept extensions to mine and will delete existing extensions at the end of June. However, blockchain-related apps are still allowed to sign in to the Store.