- Qt 6.9
- Qt WebEngine
- Qt WebEngine Security Considerations
- Qt 6.9.2 Reference Documentation

# Qt WebEngine Security Considerations

This page covers security issues for Qt WebEngine users. As part of Qt, Qt WebEngine follows Qt's security policies. Refer to Security in Qt for policy information.

## Chromium Releases and Security Fixes

Qt WebEngine tracks the release schedule of Chromium. The latest Qt WebEngine version includes the security fixes released in Chromium. For the precise version numbers and released fixes, visit the wiki page at QtWebEngine/ChromiumVersions.

For more information about how Qt WebEngine Core implements Chromium features and specific versions, read the Qt WebEngine Core Module section. It is also beneficial to be familiar with Chromium's Security Policy.

## Security Topics for Qt WebEngine Applications

Be aware of handling untrusted data and sensitive data within your application. Data such as images, user information, and system information can be loaded from remote resources, from within the application, or locally on the system. Take care how you process untrusted data in a secure way without degrading performance and exposing sensitive information. Even revealing filenames and directory paths can expose sensitive data such as system information and database structure.

Qt WebEngine and Chromium have mechanisms such as the same-origin policy to minimize the risk of loading from unknown sources. Many websites trick users with dialogues and by mimicking popular websites. With Qt WebEngine, it is possible to simply load and show trusted data to end-users and lock the interface to prevent unwanted input. Your user interface should be robust to handle erroneous inputs and unexpected events.

A serious security issue for web applications is cross-site scripting (XSS). The attack involves executing a piece of code that can trick a web application to generate malicious HTML content to gain the trust of your user. For example, your application unknowingly takes malicious code to generate a dialog asking for user credentials. Those credentials are then sent to an external service which can lead to breached accounts. Because it is your application that generates the dialog, users trust the malicious action. Be careful parsing URLs and make sure that nobody can misuse your user interface.

Refer to Handling Untrusted Data for additional information about risks and mitigation.

## Configure Qt WebEngine Settings

It is good practice to enforce zero-trust policies that restrict access by default. Configuring your Qt WebEngine deployment can help restrict user and remote execution. QWebEngineSettings has attributes that can disable JavaScript execution, disable auto-loading of images, or other mechanisms to prevent unintended usage. For example, disabling QWebEngineSettings::LocalContentCanAccessFileUrls can create a sandbox environment similar to Chrome or Firefox.