The stolen code amounts to a single file from sometime around 2003 or 2004, the company says in a blog post.

"The fact that the source code may have been publicly shared does not necessarily mean that there is any increased risk to VMware customers," according to the written by Iain Mulholland, director of the company's Security Response Center.

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The code was stolen from a Chinese company called China Electronics Import & Export Corporation (CEIEC) during a March breach, according to a on the Kaspersky Threat Post blog.

The along with internal were posted online three days ago.