In the world of updates and upgrades, it’s really important that you take the time to scan your screen for any unwanted checked boxes. How important is it? Windows-10-against-your-wishes important.

According to multiple sources, Microsoft snuck in a fun little feature in their recent important updates package: Windows 7 and 8 automatic updates users who thought they were there to get the latest bug fixes or patches were really updating to Windows 10. The company set the checkmark in the Windows 10 upgrade box by default, meaning unless you unchecked it, you could now count yourself as one of the millions who’ve upgraded.

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Microsoft swears it was an accident, according to their statement to multiple sources, including VentureBeat:

“As part of our effort to bring Windows 10 to existing genuine Windows 7 and Windows 8.1 customers, the Windows 10 upgrade may appear as an optional update in the Windows Update (WU) control panel,” a Microsoft spokesperson said. “This is an intuitive and trusted place people go to find Recommended and Optional updates to Windows. In the recent Windows update, this option was checked as default; this was a mistake, and we are removing Windows 10 from Windows Update for users that have not reserved a copy of Windows 10.”

However, Ars Technica found that even when users did bother to look over the screen carefully before blindly clicking to update, unchecking the box sent them right back into a “get started” death spiral. They had a few choices: accept the upgrade, or go hunting around online for a solution to make it stop (the third and most unattractive solution was to not update at all, leaving their systems vulnerable to whatever the update was supposed to correct).

Unfortunately, Woody Leonhard also has reason to believe it was no accident.

“In the course of researching the ongoing Windows 10 upgrade debacle for AskWoody.com, I’ve accumulated a lot of information about odd Win10 upgrade behavior on a cornucopia of PCs. In my Oct. 14 post, ‘Disable Windows 10 upgrade nagware on Windows 7, Windows 8.1 computers,’ I talk about the necessity of unchecking that ‘Upgrade to Windows 10’ box. Searching through my source material for that post, I discovered a screenshot sent in by reader JB that clearly shows the box checked on Oct 9.

“That means Microsoft checked the box on Oct. 9 or earlier — long before ‘the recent Windows update.’ This month’s Patch Tuesday, which contained more than a hundred patches, was on Oct 13.”

There’s one slick way to boost the numbers of downloads, whether users want to or not.