Security researchers discovered flaws (PDF) to the extensions systems of all modern browsers that can exploit intruders to list all installed browser extensions.
The attack affects all modern browsers. The researchers they were able to confirm this in all Chromium-based browsers and believe it also affects other browsers such as Firefox or Edge that use the same extension system. Firefox's add-on system is also vulnerable to attack.
Chromium-based browsers that are affected are Google Chrome, Yandex and Opera, and Firefox - based browsers, such as Firefox or Pale Moon and the Microsoft Edge.
All browsers protect extension data from the websites they visit. However, we have seen websites use various techniques for collection data from browsers.
Security researchers have discovered a way to help them list installed browser extensions even in the latest versions of browsers.
The "timing side-channel attack" can be used to list installed browser extensions by monitoring the browser's response to access to system resources.
When a website requests access in some resource of one extensions in the browser, the browser must perform two checks: one to see if the extension exists, and another to see if the resource the site wants to access is publicly available.
Watching the answer, the attackers may find the reason behind the refusal of a request. The site counts the time it takes to return a request from a false extension and the time it takes for a real extension.
By comparing time, installed extensions are revealed. According to the researchers, the accuracy of the method reaches 100%.
Attack uses extensions ID and some code. Researchers already have approximately 10000 Chrome and Firefox extensions identifiers. This allows them to accurately locate extensions by comparing the identifiers.
"Real" attackers could use this information for capture fingerprinting or for targeted attacks against specific browser extensions.
Since all these attacks are based on scripts, any scripts blocking can protect you from the attack.
Update: After a conversation we had on Facebook with a friend of SecNews, we were thinking of clarifying that the Apple browser is also affected: influenced by leakage URI in the Safari extensions model.
