Dominic Preston, writing at The Verge:
"Apple has reportedly been ordered by the UK government to create a backdoor that would give security officials access to users’ encrypted iCloud backups. If implemented, British security services would have access to the backups of any user worldwide, not just Brits, and Apple would not be permitted to alert users that their encryption was compromised."
Anyone reading this should turn on Advanced Data Protection, which encrypts iCloud backups, which aren't encrypted by default. There is one big caveat: You have to make doubly sure that you have your Recovery Key in a totally secure place, since you can lose your data irrevocably if you lose that key. That said, that's the reason why it's so powerful—even Apple can't decrypt your backups, even if asked by a government.
Apple ordered to open encrypted user accounts globally to UK spying
The secret order would give the UK access to encrypted backups belonging to any user — not just Brits.