As if the stability of Bitcoins wasn’t enough of a concern, now Mac OS X-based users of the cryptocurrency can lose big bucks if they aren’t careful, simply by installing a tainted app laced with malicious code.

First revealed by MacRumors, the virus, dubbed “OSX/CoinThief.A,” is a Trojan that masquerades itself as a Bitcoin app called StealthBit, which was initially uploaded to GitHub, a developer-focused site. The creator of OSX/CoinThief.A likely used the source code from GitHub to develop the malware.

Once installed, the tainted version of StealthBit installs browser extensions into Google Chrome or Safari (depending on what you use). The malicious browser add-ons then seek out login information for a multitude of Bitcoin services, including MtGox, Blockchain.com, and BTC-e. Once the iffy extensions locate your login information, it sends that data back to whomever developed the malware.

According to a poster on Reddit, someone who installed the contaminated version of StealthBit reported that they lost 20 Bitcoins. According to Bitcoin Exchangerate, 20 BitCoins is worth $13,480 as of this writing. Ouch.

If you downloaded StealthBit and you use Chrome and/or Safari for OS X, you may want to check your browser extensions for any generic-looking extensions called “Pop-up Blocker,” or anything of the sort, then purge them immediately.

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