The Tor Project has released an emergency browser update due to a problem with a key component of Tor Browser that could prevent some users from connecting to the network. The issue affects users who rely on "Snowflake" to bypass government censorship.
Snowflake is a "pluggable transport" that uses a combination of domain fronting and peer-to-peer WebRTC connections between volunteers and Tor users to circumvent Internet censorship. More than 2.5 million people use the Tor network every day to protect their privacy. The Tor network consists of all kinds of servers run by volunteers that handle the traffic of Tor users. For example, the first server is the entry guard, which forwards the Tor user's request to the relay node. It then goes from this server to the exit node, which sends the request to the Internet.
In some countries with internet censorship, providers can block Tor traffic. As a solution, Tor Browser has pluggable transports. In doing so, the Tor traffic is transformed into seemingly harmless traffic. In this way, parties that monitor the traffic do not see anything suspicious and users can still use the Tor network.
Snowflake allows Tor users in countries with internet censorship to connect to the Tor network through the browser of a volunteer in another country. All volunteers have to do is install a Chrome or Firefox extension. Also, according to the Tor Project, volunteers don't have to worry about which websites people visit through their proxy, since the visible IP address is the IP address of the exit node, not the volunteer's.
With the launch of Tor Browser 11.5.5 last Tuesday, Snowflake was further integrated into the browser. The parameters used for Snowflake turned out to be too long in this integration, leading Tor Browser to believe that no pluggable transport was set up. Users who depend on this to connect to the Tor network were therefore not able to connect. The Tor Project has now released an "emergency release" to fix the problem. Users are therefore advised to update to Tor Browser 11.5.6.