You need to update Firefox right now to protect yourself from a big security flaw

If you use FireFox you will want to make sure you have the latest update installed.

Mozilla is warning users that a FireFox exploit has been found in the wild that can search and steal files from your computers without you ever having any idea.

Mozilla published a blog post on its website describing the vulnerability and encouraged users to make sure their software was updated. A fix was rolled out in Firefox 39.0.3 and in Firefox ESR 38.1.1.

The vulnerability affects desktop versions of Firefox software.

The problem stems "from the interaction of the mechanism that enforces JavaScript context separation (the "same origin policy") and Firefox's PDF Viewer," according to the blog post. This means that Firefox software that does not contain the PDF viewer, like its Android version, are not affected.

"The exploit leaves no trace it has been run on the local machine. If you use Firefox on Windows or Linux it would be prudent to change any passwords and keys found in the above-mentioned files if you use the associated programs," Mozilla stated in its blog post.

The company also said that users who use ad-blocking software may be protected from this exploit depending on the software and the filter settings being used.