The advice comes from antivirus firm, Bitdefender following the discovery that the Opera homepage was loading malicious obfuscated scripts that would redirect users to a third-party page housing the infamous BlackHole exploit kit for “at least a few hours” on Wednesday.
Bitdefender says that the exploit code was likely loaded through a third-party advertisement, a practice called “malvertising.”
During their analysis, Bitdefenders found that the BlackHole exploit kit used a PDF file rigged with the CVE-2010-0188 exploit to drop a new Zbot variant, detected as Trojan.Zbot.HXT, onto the affected machine.
The obfuscated script associated with this attack is detected as Trojan.Script.478548.
Opera has since disabled the ads on the browser’s homepage while they investigate what happened.
So far there have not been any reports of infections stemming from this attack.