It's probably stored in plaintext, unsecured with the user's Mozilla account (whose password is also used to unsecure his stored passwords and browser history,

It's probably stored in plaintext, unsecured with the user's Mozilla account (whose password is also used to unsecure his stored passwords and browser history, which means that if he hands his information to his buddy or secretary to enable him to update a page, he'll also be handing that buddy or secretary his entire online identity). But maybe I'm wrong, and it's stored in an encrypted hash-addressed data store, where shared links include the necessary keys. There are levels of security; it's fine for Webmaker not to be suitable for, e.g., human-rights activists in Burma. But it should not be possible for one data breach to reveal everyone's activity everywhere.