During the past few days some of our users have contacted us raising the concern that the Qihoo 360 Total Security anti-virus software has been labelling the Opera installer executable for Windows as some form of malware (HEUR/QVM11.1.0000.Malware.Gen).
The installer setup that we provide at opera.com is digitially signed by us, and we can assure our users that the installer executable does not contain any malicious code. Following these reports, we tested the executable with various anti-virus software products and only a single product was marking the installer as malicious.
As soon as we noticed this false positive, we reached out to the anti-virus software vendor in order to clear the issue. We understand that anti-virus software products are sometimes extra-vigilant in their heuristics, which might not necessarily be triggered by malicious factors only. There could be legitimate cases where some of the behaviour of setup executables could trigger these heuristics and it is not uncommon for this to happen.
We hope our users understand that this is a false warning from 360 Total Security software, and we assure you that we will try our best to resolve this.