Is it a single file or a folder. Please mention the file name

It is a single file located in the cache folder of Firefox browser and the file name is: E89FCd01

Hello <!-- XXX you may wish to edit this greeting, and other parts of the response so that it is personalised to the question asked.--> , Certain Firefox problems can be solved by performing a ''Clean reinstall''. This means you remove Firefox program files and then reinstall Firefox. Please follow these steps: '''Note:''' You might want to print these steps or view them in another browser. #Download the latest Desktop version of Firefox from http://www.mozilla.org and save the setup file to your computer. #After the download finishes, close all Firefox windows (click Exit from the Firefox or File menu). #Delete the Firefox installation folder, which is located in one of these locations, by default: #*'''Windows:''' #**C:\Program Files\Mozilla Firefox #**C:\Program Files (x86)\Mozilla Firefox #*'''Mac:''' Delete Firefox from the Applications folder. #*'''Linux:''' If you installed Firefox with the distro-based package manager, you should use the same way to uninstall it - see [[Installing Firefox on Linux]]. If you downloaded and installed the binary package from the [http://www.mozilla.org/firefox#desktop Firefox download page], simply remove the folder ''firefox'' in your home directory. #Now, go ahead and reinstall Firefox: ##Double-click the downloaded installation file and go through the steps of the installation wizard. ##Once the wizard is finished, choose to directly open Firefox after clicking the Finish button. More information about reinstalling Firefox can be found [[Troubleshoot and diagnose Firefox problems#w_5-reinstall-firefox|here]]. <b>WARNING:</b>Do not use a third party uninstaller as part of this process. Doing so could permanently delete your [[Profiles|Firefox profile]] data, including but not limited to, extensions, cache, cookies, bookmarks, personal settings and saved passwords. <u>These cannot be easily recovered unless they have been backed up to an external device!</u> See [[Back up and restore information in Firefox profiles]]. <!-- Starting in Firefox 31, the Firefox uninstaller no longer lets you remove user profile data.Ref: Bug 432017 and https://support.mozilla.org/kb/uninstall-firefox-from-your-computer/discuss/5279 [Fx31] Windows uninstaller will no longer offer the option to remove personal data --> Please report back to say if this helped you! Thank you.

See also: *https://support.mozilla.org/kb/Firefox+cache+file+was+infected+with+a+virus

A uninstall and reinstall as suggested by iamjayakumars is a waste of time in this case. The viruses/Trojans and other such files found in Cache is harmless unless you manually try and run them and they will get overwritten over time anyways unless you manually cleared Cache. Sometimes a recent definition update can cause false positives and another update is needed.