Replaced code signing certificate

Opera Software recently experienced an attack on the internal infrastructure. Following best practices, Opera Software is replacing signing certificates in Opera with newly issued certificates. Certificates in Opera include the code signing certificate for desktop binaries and the signing...

The wrong executable may be used to display a downloaded file in its folder

Opera's downloads manager allows users to select a file, and open the folder containing that file. This file will be opened using the operating system's file system viewer. In some cases, Opera will use the wrong executable when trying to show the folder view, and that executable may execute code...

Issue with error pages can cause a system crash

When attempting to resolve a URL which cannot be interpreted as a legal URL, Opera will create an error page to display to the user when they load it. If enough invalid URLs can be created, Opera can use up all available disk space with these error pages, causing the browser or operating system t...

Element HTML content can be incorrectly returned without escaping, bypassing some HTML sanitizers

When sites accept HTML from untrusted users, and use that HTML as page content, they typically sanitize the untrusted HTML to ensure that it does not contain any harmful content, such as malicious scripts. In some cases, this sanitization may be performed by writing and reading the contents of DO...

TLS response timings can indicate network contents

When Opera receives incorrectly encrypted network data, Opera will detect this, and let the sender know that the data was not understood. Such encrypted error responses are marginally faster than regular responses. An attacker with access to the network, can by replacing network data measure...

Cookies can be set for a top-level domain

Browsers should only allow cookies to be set for the website that created them. In some specific cases, Opera does not apply this restriction correctly, and allows a website to set a cookie for its entire top-level domain such as .com or .co.uk. A malicious site could then redirect the user to...

Plug-in content may monitor keystrokes on unrelated pages

Plug-ins may use operating system features to detect key presses when the plug-in is focused. If the plug-in does not detect its own focused state correctly, it can detect key presses when other pages are focused, allowing the plug-in content to detect key presses intended for pages from other...

History.state can leak the state data from cross domain pages

When a site uses history.pushState and history.replaceState to add or replace history entries, it can also provide optional data, which may typically be used to restore the given state when the user navigates through their browser history. When pages with cross-domain frames use this functionalit...

RC4 encryption protocol is vulnerable to certain brute force attacks

Weaknesses in the RC4 encryption protocol have been found, allowing an attacker to deduce the plaintext. If the same message is encrypted many millions of times, statistical methods can be used to extract valuable information, such as cookies. Due to the time this amount of requests takes, this i...

DOM events manipulation might be used to execute arbitrary code

Particular DOM event manipulations can cause Opera to crash. In some cases, this crash might occur in a way that allows execution of arbitrary code. To inject code, additional techniques would have to be employed...

Clickjacking attacks may be carried out against internal opera: URLs

Internal opera: URLs which may be used to modify the Opera configuration have some intentional restrictions that are designed to mitigate possible clickjacking attacks. Certain manipulations can trick Opera into bypassing those restrictions, which would then allow clickjacking attacks to be carri...

HTTP response heap buffer overflow can allow execution of arbitrary code

When requesting pages using HTTP, Opera temporarily stores the response in a buffer. In some cases, Opera may incorrectly allocate too little space for a buffer, and may then store too much of the response in that buffer. This causes a buffer overflow, which in turn can lead to a memory corruptio...

Cross domain access to object constructors can be used to facilitate cross-site scripting

JavaScripts are able to redefine and override the methods of native objects. They may also do this with the native objects of any document that shares the same origin. By redefining the methods of another document through the constructor property of the document's host objects, a malicious script...

Certain URL constructs can allow arbitrary code execution

Certain page address URL constructs can cause Opera to allocate the wrong amount of memory for storing the address. When it then attempts to store the address, it will overwrite unrelated memory with attacker-controlled data. This can lead to a crash, which may also execute that data as code...

Error pages can be used to guess local file paths

Remote web pages should not be able to detect what files a user has on their local machine. Certain error pages do not apply this restriction correctly, allowing web pages to produce an error page where a script can run. The script can then use various events to detect whether files on the user's...

Certificate revocation service failure may cause Opera to show an unverified site as secure

When accessing secure websites, Opera checks with a number of services to check if the website's security certificate has been revoked. Normally, if Opera cannot check revocation status, it will not present the site as secure. In some cases, a failure in one of these services can cause Opera not ...

Web page content may overlap the address field

The browser's user interface contains several pieces of security information. To preserve this information correctly, web page content should not be able to display over the user interface. Certain styling can cause Opera to allow the content to be displayed outside the page, over the address...

Specially crafted SVG images can allow execution of arbitrary code

Opera can display images created using the Scalable Vector Graphics SVG format. Specially crafted and malformed SVG images may cause Opera to crash when their documents are unloaded, and the crash may allow execution of malicious arbitrary code. To inject code, additional techniques will have to ...

Web pages can gain limited access to files on the user's computer

Certain types of HTTP responses and redirections can cause Opera to mistakenly give elevated privileges to remote web pages. These pages can then use their elevated privileges to load files from the user's computer as web page resources. This may allow scraping of potentially sensitive informatio...

Truncated dialogs may be used to trick users

When an important dialog is being displayed, such as a download dialog, the entire dialog should be visible, so that the user can clearly see what the dialog's buttons will do. In some cases, specific user interactions can cause Opera not to enforce this correctly, allowing the window to become...

Carefully timed reloads, redirects, and navigation can spoof the address field

The address field should always show the address of the page that is being displayed. Certain types of navigation, combined with reloads and redirects to a slowly-responding target site can cause the address field to show the target site's address, while the attacking site is still being displaye...

Overlapping content can trick users into executing downloads

Dialogs such as the download dialog are usually displayed on top of page content, to ensure that the user knows that the dialog is requesting attention. In some cases, this policy was not implemented correctly in Opera, allowing certain page content to overlay the dialog. In these cases, clicking...

Cross-domain JSON resources may be exposed as JavaScript variable data

JSON strings are sometimes exported by sites as a resource that cannot be read cross-domain, and may contain confidential data. The format of a JSON string ensures that it cannot be read as the contents of a variable, if it is included as a normal script. In some cases, Opera does not correctly...

Carefully timed reloads and redirects can spoof the address field

The address field should always show the address of the page that is being displayed. In certain cases, if a target site responds slowly, reloading an attacking page and redirecting to the target page can cause the address field to show the target site's address, while the attacking site is still...

Certain DOM manipulations can allow execution of arbitrary code

Various unexpected DOM manipulations can cause Opera to crash. In some cases, these crashes can occur in a way that allows execution of arbitrary code. To inject code, additional techniques may have to be employed...

Web page content can display misleading security information

Dialogs such as the security information dialog and download dialog are displayed over the top of the webpage content. In some cases, webpage content will be incorrectly displayed on top of the dialogs, or over parts of the dialogs. This content can then display misleading security information,...

Small windows can be used in several ways to trick users into executing downloads

When the download dialog is displayed, it should always be visible to the user, to ensure that the user realizes it is there. If the dialog is displayed in a small enough window, the user may not realize it is being displayed, and if the right keyboard sequence is carefully followed, they can end...

Hidden keyboard navigation can allow cross site scripting or code execution

When a user is interacting with a window, that window should be visible to the user, to ensure that the user realizes it is there. If a page is displayed in a small enough window, the user may not realize it is being displayed, and if the right keyboard sequence is carefully followed, they can en...

Pages can prevent navigation to a target page, spoofing the address field

When a user types a new URL for the browser to load, the currently active page may detect when the new page is about to load and prevent the navigation, while still leaving the new URL displayed in the address bar. This can then be used to spoof the URL of the target page. The malicious page woul...

Data URIs may be used to initiate cross site scripting against unrelated sites

Data URIs are supposed to inherit the security context from the page that created them. In some cases, Opera does not enforce this correctly, and will allow unrelated data URIs to interact both with each other, and their source pages. This can be used to enable cross site scripting against the...

Large form inputs can allow execution of arbitrary code

When certain large form inputs appear on a web page, they can cause Opera to crash. In some cases, the crash can lead to memory corruption, which could be used to execute code. To inject code, additional techniques will have to be employed...

JavaScript might run in the wrong context if loaded from error page

If Opera is sent to an invalid URL, an error page will be displayed along with a link to the URL. The URL linked to might run scripts, and in some cases these scripts might be run in the wrong security context. This can be used to execute scripts in the context of an unrelated domain, which allow...

A combination of clicks and key presses can lead to cross site scripting or code execution

When a user double clicks on a page, they may expect the two clicks to target the same object. If a page uses the first click to open a pop-up window in a predictable location, the second click may focus parts of the new window, such as its address field. If the page can then convince the user to...

Internet shortcuts used for phishing in <img> elements

Websites may occasionally want to display image content from untrusted sources. A phishing attack may be carried out by the untrusted source, by displaying malicious instructions on the image, or by navigating the containing page to a similar looking document on another server. Since some image...

Small windows can be used to trick users into executing downloads

When the download dialog is displayed, it should always be visible to the user, to ensure that the user realizes it is there. If the dialog is displayed in a small enough window, the user may not realize it is being displayed, and if the right keyboard sequence is carefully followed, they can end...

Printing issue can allow data leaks to other system users, or allow them to corrupt data

When pages are printed by Opera, a temporary file is created, which contains the document to print. This document is not created with the correct permissions, allowing other users of the system to read its contents. When printed with certain popular printing frameworks, an additional temporary fi...

Use of SVG clipPaths can allow execution of arbitrary code

When SVG documents with specifically prepared clipPaths are used in Opera, Opera may allow other content to overwrite the memory, before referencing the memory, which will lead to a crash. If an attacker can control the contents being written into memory, execution of arbitrary code may occur...

Data URIs can be used to facilitate Cross-Site Scripting

Data URIs are only supposed to inherit the scripting origin from the site that creates them, such as by including them as the target of a link or an inline frame in the source of the document. Specific sequences of document and data URI loading can cause Opera to forget which document created the...

Email passwords are not immediately deleted when deleting private data

When using "Delete Private Data" and selecting the option to "Clear all email account passwords", the passwords were not deleted immediately, and would continue to be used until the browser was restarted. This could unexpectedly allow continued access to those email accounts...

Private data can be disclosed to other computer users, or be modified by them

Private data such as cache, password files, and Opera's configuration files are supposed to be visible only to the user who owns the Opera profile. Opera does not set the profile folder permissions correctly, allowing other computer users to read the sensitive contents of profile files. In some...

Specially crafted WebP images can be used to disclose random chunks of memory

WebP images may be used as fill patterns in a HTML5 Canvas, and the values of each pixel in the image can then be intentionally read using scripts. Specially crafted WebP images may specify the wrong size for certain parts of their data, which causes Opera to read data from the wrong positions in...

Web page dialogs can be used to to display the wrong address in the address field

The address field should always show the correct address for the page that is loaded. If a page can cause Opera to display certain dialogs relating to a target site, the dialog may in some cases cause Opera to display the target site's address instead of the correct address. This can allow an...

Malformed GIF images could allow execution of arbitrary code

When loading GIF images into memory, Opera should allocate the correct amount of memory to store that image. Specially crafted image files can cause Opera to allocate the wrong amount of memory. Subsequent data may then overwrite unrelated memory with attacker-controlled data. This can lead to a...

CORS requests can omit the preflight request

Cross-Origin Resource Sharing CORS requests are required to send a preflight request if custom headers are included, to check that the host wishes to allow the full request to be made. An example of where this may be needed is for sites that use a custom header with a static value as part of thei...

Carefully timed redirects can allow cross site scripting

Scripts on a page are supposed to be restricted so that they can only interact with other pages from the same domain and security context. Carefully timed redirects can cause scripts to execute in the wrong security context in Opera. This allows cross site scripting XSS...

Certain characters in HTML can incorrectly be ignored, which can facilitate XSS attacks

Sites that allow content to be provided by untrusted users, such as forums and blogging sites, typically sanitize the untrusted content to ensure that it does not contain any harmful content, such as malicious scripts. When certain characters appear at specific locations within HTML markup, they...

WAP form content can be leaked to other sites

When accepting user input in form fields on a WAP page, WML requires that the input contents are remembered, and used to populate every further input sharing the same name. This should continue as long as the user continues to click links known as a WAP session, even populating similarly named...

Repeated attempts to access a target site can trigger address field spoofing

The browser address field should always show the correct address for the page that is currently being displayed. By making repeated requests to load a target site in rapid succession, an attacking web site can cause Opera to display the target sites address while the attacking page is still being...

CORS requests can incorrectly retrieve contents of cross origin pages

CORS Cross-Origin Resource Sharing allows web pages to retrieve the contents of pages from other sites, with their permission, as they would appear for the current user. When requests are made in this way, the browser should only allow the page content to be retrieved if the target site sends the...

Frameset issue allows execution of arbitrary code

Framesets allow web pages to hold other pages inside them. Certain frameset constructs are not handled correctly when the page is unloaded, causing a memory corruption. To inject code, additional techniques will have to be employed...