Opera before 7.54 allows remote attackers to modify properties and methods of the location object and execute Javascript to read arbitrary files from the client's local filesystem or display a false URL to the user.

Opera allows remote attackers to cause a denial of service (invalid memory reference and application crash) via a web page or HTML email that contains a TBODY tag with a large COL SPAN value, as demonstrated by mangleme.

Opera does not prevent cookies that are sent over an insecure channel (HTTP) from also being sent over a secure channel (HTTPS/SSL) in the same domain, which could allow remote attackers to steal cookies and conduct unauthorized activities, aka "Cross Security Boundary Cookie Injection."

Opera 7.51 for Windows and 7.50 for Linux does not properly prevent a frame in one domain from injecting content into a frame that belongs to another domain, which facilitates web site spoofing and other attacks, aka the frame injection vulnerability.