This vulnerability was a potential CSRF attack. When running the Firebase emulator suite, there is an export endpoint that is used normally to export data from running emulators. If a user was running the emulator and navigated to a malicious website with the exploit on a browser that allowed calls to localhost (ie Chrome before v94), the website could exfiltrate emulator data. We recommend upgrading past version 13.6.0 or commit  068a2b08dc308c7ab4b569617f5fc8821237e3a0 https://github.com/firebase/firebase-tools/commit/068a2b08dc308c7ab4b569617f5fc8821237e3a0