A popular browser extension that helps personalize how a website looks has been found to be tracking user activity. The revelation has pushed Google and Mozilla to remove the Stylish browser extension from their app stores. However, the extension’s official website still remains active.

Software engineer Robert Heaton claimed in a blog post that the Stylish extension tool steals a user’s internet history and sends information about a person’s browsing history and distinct identifiers to SimilarWeb, the extension’s owner. According to Heaton, this will allow the company to “connect all of an individual’s actions into a single profile.”

Use this popular Chrome, Firefox add-on? Google, Mozilla just banished it https://t.co/S4rxlNJbMi @LiamT pic.twitter.com/dujWinaIRb

— ZDNet (@ZDNet) July 6, 2018

Heaton further explained that Stylish account holders typically have a unique identifier that can be linked to a login cookie. This will then provide SimilarWeb with enough information to “theoretically tie these histories to email addresses and real-world identities.”

Stylish is an open-source browser extension that gives users the capability to change how a website appears on their browser. With it, users can make websites look brighter and campier. They can also go for a brooding, darker theme or choose popular manga or cartoon characters to add to the website.

SimilarWeb’s 2017 formal policy does indicate that the extension collates anonymous data. But what Heaton is protesting is the identifier that the extension attaches to the said information before it’s sent to the company servers. He said this leaves the account holder vulnerable to hackers.

SimilarWeb has already denied these allegations and claimed that they are “not aware of and cannot determine the identity of the users from whom the non-personal information is collected.”

Google and Mozilla have since removed the extension from its Chrome and FireFox browsers. The former has not explained its decision to cut off Stylish while the latter said that they blocked the extension due to violation of data practices.

Users utilizing Stylish on their web browsers would no longer be able to access its features. However, the extension remains active online.

[Featured image via Pixabay]