Apple's OSX 10.10 – aka Yosemite – is silently uploading users' unsaved documents and the email addresses of their contacts to Apple's iCloud, according to security researcher Jeffrey Paul.

Berlin-based Paul said the discovered the document auto-syncing without consent issue, and another hacker expanded the point by discovering that email contact addresses were also getting saved.

iCloud technology pre-dates the release of Yosemite but Apple has changed the way it works to remove the save/delete “What do you want to do with this file?” prompt.

A traffic log of Yosemite carrying out auto-save to iCloud has been posted online and available here. "Unsaved documents are automatically uploaded to iCloud *before* the user has selected where they would like the document to be saved," open source developer Landon Fuller reports.

The changes can be reversed and auto-saving disabled by going adjusting the options in the system preferences in Macs (> System Preferences, iCloud, uncheck Documents & Data).

Nonetheless, security researchers such as Nadim Kobeissi and others are critical of Apple's changes.

Upgrading to Yosemite has also broken a minority of users' Wi-Fi connections, as explained in a blog post by Sophos here. The cause of, much less the solution to, the wireless access problem remains unclear at the time of writing.

Last week it emerged that the Spotlight search feature in Yosemite was passing on location and search data to Apple and its partners. Like the iCloud data syncing without permission the feature can be disabled in system preferences.

Security watchers have been almost unanimous in arguing it would be best to let users opt-in to these features. OS X Yosemite encrypts disks by default, better protecting privacy, but the plaudits Apple has received for FileVault disk encryption have been all but drowned out by criticisms of the iCloud changes.

Apple had yet to comment on the issue at the time of publication.®