Opera 8.01, when the "Arial Unicode MS" font (ARIALUNI.TTF) is installed, does not properly handle extended ASCII characters in the file download dialog box, which allows remote attackers to spoof file extensions and possibly trick users into executing arbitrary code.

Opera 8.01 allows remote attackers to conduct cross-site scripting (XSS) attacks or modify which files are uploaded by tricking a user into dragging an image that is a "javascript:" URI.

A design error in Opera 8.01 and earlier allows user-assisted attackers to execute arbitrary code by overlaying a malicious new window above a file download dialog box, then tricking the user into double-clicking on the "Run" button, aka "link hijacking".

Opera 8.01 allows remote attackers to cause a denial of service (CPU consumption) via a crafted JPEG image, as demonstrated using random.jpg.

Opera 7.x and 8 before 8.01 does not clearly associate a Javascript dialog box with the web page that generated it, which allows remote attackers to spoof a dialog box from a trusted site and facilitates phishing attacks, aka the "Dialog Origin Spoofing Vulnerability."

The XMLHttpRequest object in Opera 8.0 Final Build 1095 allows remote attackers to bypass access restrictions and perform unauthorized actions on other domains via a redirect.

Cross-site scripting (XSS) vulnerability in Opera 8.0 Final Build 1095 allows remote attackers to inject arbitrary web script or HTML via "javascript:" URLs when a new window or frame is opened, which allows remote attackers to bypass access restrictions and perform unauthorized actions on other domains.

Format string vulnerability in the a_Interface_msg function in Dillo before 0.8.3-r4 allows remote attackers to execute arbitrary code via format string specifiers in a web page.

The International Domain Name (IDN) support in Opera 7.54 allows remote attackers to spoof domain names using punycode encoded domain names that are decoded in URLs and SSL certificates in a way that uses homograph characters from other character sets, which facilitates phishing attacks.

Opera 7.54 and earlier on Gentoo Linux uses an insecure path for plugins, which could allow local users to gain privileges by inserting malicious libraries into the PORTAGE_TMPDIR (portage) temporary directory.