Error Events

CORB Leaks

October 1, 2020
Abuse Browser Feature, Error Events, Content-Type, nosniff
Category Attack
Defenses Fetch Metadata, SameSite Cookies

Cross-Origin Read Blocking (CORB) is a web platform security feature aimed at reducing the impact of speculative side-channel attacks such as Spectre. Unfortunately, blocking certain types of requests introduced a new type of XS-Leaks 1 that allows attackers to detect if CORB was enforced on one request, but wasn’t on another. Nevertheless, the introduced XS-Leaks are much less problematic than the issues actively protected by CORB (e.g. Spectre). info ...

Error Events

October 1, 2020
Abuse Error Events, Status Code, nosniff, Content-Type
Category Attack
Defenses Fetch Metadata, SameSite Cookies

When a webpage issues a request to a server (e.g. fetch, HTML tags), the server receives and processes this request. When received, the server decides whether the request should succeed (e.g. 200) or fail (e.g. 404) based on the provided context. When a response has an error status, an error event is fired by the browser for the page to handle. These errors also cover situations where the parser fails, for example when trying to embed HTML content as an image. ...

Cache Probing

Abuse window.open, Error Events, Cache, iframes, AbortController
Category Attack
Defenses SameSite Cookies, Vary: Sec-Fetch-Site, Subresource Protections

The principle of Cache Probing consists of detecting whether a resource was cached by the browser. The concept has been known since the beginning of the web 1 and initially relied on detecting timing differences. When a user visits a website, some resources such as images, scripts, and HTML content are fetched and later cached by the browser (under certain conditions). This optimization makes future navigations faster as the browser serves those resources from disk instead of requesting them again. ...