Opera is giving users the standard upgrade advice after a successful attack on its network allowed evil-doers to copy a software-signing certificate.
As a result, they would be able to craft malware that would authenticate as coming from Opera.
In this blog post, Opera's Sigbjørn Vik explains that the software company identified and halted the attack on June 19. Although it's confident that “there is no evidence of user data being compromised … the attackers were able to obtain at least one old and expired Opera code signing certificate, which they have used to sign some malware.”
Opera believes the impact is limited to “a few thousand Windows users” who may have automatically received and subsequently installed the malware. Opera directs users to Virustotal for an overview of which packages will detect the malware.
In spite of the reassuring tone of the post, Sophos' Paul Ducklin notes that the attackers apparently managed to upload at least one malicious file back into Opera's servers.
Opera says it is now working to ship an update of its browser, and advises users to install it as soon as it becomes available. ®