How to organize secure inter-process communication between an extension and external websites or native applications?
Modern browser extensions frequently need to exchange data with external web resources or local programs on the user's computer. To communicate with third-party sites, the external messaging mechanism is used, which allows web pages to send messages to specific extensions by their IDs. To keep this communication channel secure, the developer must clearly configure the field in the manifest that defines the list of trusted domains. Without such filtering, a malicious site could send commands to your extension, leading to vulnerabilities.
To interact with native operating system applications, the Native Messaging technology is used. It utilizes a special host process running in the background on the OS side, with which the extension exchanges messages via standard input-output streams. The browser acts as a gateway isolating the extension environment from direct interaction with the operating system. When designing such communication, it is critically important to verify data authenticity on both sides and use digital signatures for native host executables to prevent component spoofing by attackers.
The process of implementing secure data exchange requires adherence to the following basic principles:
Compliance with these rules reduces the risk of cross-site scripting (XSS) attacks and unauthorized control of extension functions by compromised web resources.