When Firefox 60 releases, it will introduce support for the same-site cookie attribute in an effort to protect users against cross-site request forgery (CSRF) attacks.
CSRF attacks allow attackers to perform unauthorized activities on a website on behalf of authenticated users by getting them to visit a specially crafted webpage. These types of attacks leverage the fact that every request to a website includes cookies and many sites rely on these cookies for authentication purposes.
Mozilla, which operates Firefox, said the current web architecture does not allow websites to reliably determine if a request has been initiated legitimately by the user or if it comes from a third-party script.
“To compensate, the same-site cookie attribute allows a web application to advise the browser that cookies should only be sent if the request originates from the website the cookie came from,” members of the Mozilla Security Team said in a post. “Requests triggered from a URL different than the one that appears in the URL bar will not include any of the cookies tagged with this new attribute.”
Firefox 60, currently scheduled for release May 9, will attempt to protect users against CSRF attacks with same-site attributes that can have one of two values: Strict or lax.
In strict mode, when users click on an inbound link from an external site, they will be treated as unauthenticated even if they have an active session as cookies will not be sent.
In lax mode, cookies will be sent when users navigate safely from an external website (e.g. by following a link), but they will not be sent on cross-domain subrequests, such as the ones made for images or frames. The lax mode is designed for applications that may be incompatible with the strict mode.