Opera before 57.0.3098.106 is vulnerable to a DLL Search Order hijacking attack where an attacker can send a ZIP archive composed of an HTML page along with a malicious DLL to the target. Once the document is opened, it may allow the attacker to take full control of the system from any location within the system. The issue lies in the loading of the shcore.dll and dcomp.dll files: these files are being searched for by the program in the same system-wide directory where the HTML file is executed.

Characters from languages are such as Arabic, Hebrew are displayed from RTL (Right To Left) order in Opera 37.0.2192.105088 for Android, due to mishandling of several unicode characters such as U+FE70, U+0622, U+0623 etc and how they are rendered combined with (first strong character) such as an IP address or alphabet could lead to a spoofed URL. It was noticed that by placing neutral characters such as "/", "?" in filepath causes the URL to be flipped and displayed from Right To Left. However, in order for the URL to be spoofed the URL must begin with an IP address followed by neutral characters as omnibox considers IP address to be combination of punctuation and numbers and since LTR (Left To Right) direction is not properly enforced, this causes the entire URL to be treated and rendered from RTL (Right To Left). However, it doesn't have be an IP address, what matters is that first strong character (generally, alphabetic character) in the URL must be an RTL character.

Opera cannot properly restrict modifications to cookies established in HTTPS sessions, which allows man-in-the-middle attackers to overwrite or delete arbitrary cookies via a Set-Cookie header in an HTTP response, related to lack of the HTTP Strict Transport Security (HSTS) includeSubDomains feature, aka a "cookie forcing" issue.

Opera before 10.10 permits cross-origin loading of CSS stylesheets even when the stylesheet download has an incorrect MIME type and the stylesheet document is malformed, which allows remote attackers to obtain sensitive information via a crafted document.

Opera executes DOM calls in response to a javascript: URI in the target attribute of a submit element within a form contained in an inline PDF file, which might allow remote attackers to bypass intended Adobe Acrobat JavaScript restrictions on accessing the document object, as demonstrated by a web site that permits PDF uploads by untrusted users, and therefore has a shared document.domain between the web site and this javascript: URI. NOTE: the researcher reports that Adobe's position is "a PDF file is active content."

Sun Java Runtime Environment (JRE) in JDK and JRE 6 Update 2 and earlier, JDK and JRE 5.0 Update 12 and earlier, SDK and JRE 1.4.2_15 and earlier, and SDK and JRE 1.3.1_20 and earlier, when Firefox or Opera is used, allows remote attackers to violate the security model for JavaScript outbound connections via a multi-pin DNS rebinding attack dependent on the LiveConnect API, in which JavaScript download relies on DNS resolution by the browser, but JavaScript socket operations rely on separate DNS resolution by a Java Virtual Machine (JVM), a different issue than CVE-2007-5273. NOTE: this is similar to CVE-2007-5232.