The child frames in Opera 9 before 9.20 inherit the default charset from the parent window when a charset is not specified in an HTTP Content-Type header or META tag, which allows remote attackers to conduct cross-site scripting (XSS) attacks, as demonstrated using the UTF-7 character set.
Opera allows remote attackers to cause a denial of service (application crash) via a web page that contains a large number of nested marquee tags, a related issue to CVE-2006-2723.
The Javascript SVG support in Opera before 9.10 does not properly validate object types in a createSVGTransformFromMatrix request, which allows remote attackers to execute arbitrary code via JavaScript code that uses an invalid object in this request that causes a controlled pointer to be referenced during the virtual function call.