Source: Firebase Realtime Database Supports SSL Certificate Transparency from Firebase
Here at Firebase, we work hard to keep your apps secure and protect your users. In keeping with that mission, we’re proud to announce that we recently implemented Certificate Transparency for the Realtime Database.
Certificate Transparency makes it possible to detect SSL certificates that have been mistakenly issued by a certificate authority. It also makes it possible to identify certificate authorities that have gone rogue and are maliciously issuing certificates. These attack vectors are rare but serious ways of circumventing the protections that SSL/TLS grant to online communication.
Part of Certificate Transparency is the issuance of a Signed Certificate Timestamp (SCT), which Realtime Database responses now include. We have already been sending the SCT when browsers like Chrome requested it, but now it is always bundled in the response.
From today on, every connection from one of your users to your database will be protected by the SCT. Please be aware that the SCT creates a little more SSL overhead, so each response gets slightly larger. The percentage increase for your app is dependent on many factors, such as your average response size, and which clients your customers use. Since outgoing bandwidth (egress) is billed, you may see a slight bill increase as a result.
Certificate Transparency is a great enhancement to SSL/TLS, and we Firebasers are excited about what it means for the security of the internet going forward. We’re delighted to bring this protection to you and your users.