Apple has said it is aware of an email encryption bug in macOS Catalina, and that it plans to fix the problem in a future update.
As reported by The Verge, a vulnerability was discovered by Apple IT-specialist Bob Gendler in Apple’s Mail application for macOS. Whilst exploring how macOS and Siri curates information to suggest to users, he discovered that Mail and other apps store information which Siri uses to tailor its suggestions. One file, snippets.db, was apparently storing unencrypted text of emails that should have been encrypted. Even after removing the private key so as to prevent him reading encrypted emails, he found that the text of the email could still be viewed in snippets.db. The problem reportedly affects Catalina, Mojave, High Sierra, and Sierra.
According to the report:
Apple tells The Verge it’s aware of the issue and says it will address it in a future software update. The company also says that only portions of emails are stored. But the fact that Apple is still somehow leaving parts of encrypted emails out in the open when they’re explicitly supposed to be encrypted, obviously isn’t good.
The Verge also notes that the issue, whilst concerning, may have only affected a very small number of people.
You need to be using macOS, Apple Mail, be sending encrypted emails from Apple Mail, not be using FileVault to encrypt your entire system already, and know exactly where in Apple’s system files to be looking for this information. If you were a hacker, you’d need access to those system files, too.
You can stop Siri collecting emails in snippets.db by going to System Preference > Siri > Siri Suggestions and Privacy > Mail. Simply unselect “Learn From this App.” Gendler suggests that this will not remove any older emails that may have already been stored, those will need to be deleted manually. Turning on FileVault will also ensure everything on your Mac is encrypted.
As The Verge notes, this vulnerability won’t affect many people but does call into question Apple Mail’s encryption. Gendler also said:
“It brings up the question of what else is tracked and potentially improperly stored without you realizing it.”