A popular plugin was recently cloned and downloaded more than 37,000 before people caught on. Over 1,400 counterfeit versions of the extension have been reported over the past two years, across all browsers. Adblock claims only 900 of these have been removed.

Adblock, maker of the web’s most popular ad-blocking plugin, declared that the imitation was detected and reported to Google on September 14, but was only taken down on October 6.

The company took its own precautions to raise awareness of the problem, publishing an explainer on its blog. The post explains that many counterfeit versions are apps, and not extensions of Google Chrome, as Adblock Plus is.

Adblock stated, “For its part, Adblock Plus pays for an independent monitoring company to scan all the download portals and web stores to ensure that its products are safe.” This means anyone who gets tricked into downloading a fake version is also at risk of downloading any extra, dangerous material onto their computer.

Google has made an effort since at least 2015 to detect and remove fake versions of popular plugins by restricting PC users from downloading extensions from outside Chrome’s official marketplace. Still, this continues to be a problem.

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