If you're running Android Oreo you should probably keep an eye on your mobile-data usage until Google fixes a bug that causes phones to use mobile data even when they are connected to Wi-Fi.
A number of Oreo users are experiencing this issue, flagged yesterday by Redditor Unusual_Sauce. After installing Oreo on a Pixel XL, the device began preferring mobile data even when Wi-Fi was turned on and a Wi-Fi network was available, according to Unusual_Sauce.
"After updating to Oreo last night, I received a huge spike in data usage, all the while being connected to Wi-Fi. I contacted support and was told that they are aware of the issue and are working on a fix. In the meantime I have turned off mobile data while at home, so only Wi-Fi is being used," Unusual_Sauce wrote.
Google's support staff have received reports from other users with the same issue, according to the Redditor.
A bug like this could be a minor annoyance for those on unlimited mobile plans but costly for anyone on a limited plan if they're penalized for exceeding their monthly limit.
The problem appears to stem from Mobile Data Always Active, a setting available in Developer Options. Normally this setting is disabled by default, but installing Oreo results in it being enabled by default.
According to one user, Google for some reason enabled the setting by default during the Oreo developer preview, but didn't change it back before general release.
Fortunately, very few Android users will be affected, given Oreo is currently only available as an OTA for Pixel and Nexus phones as well as Verizon's Pixel and Pixel XL devices.
Until Google delivers a fix, Oreo users can go to Developer Options and disable Mobile Data Always Active" to make sure the device isn't using mobile data unnecessarily.
Google is also investigating reports that Bluetooth in Android Oreo isn't connecting properly to car audio systems, headphones and speakers. The issue affects Pixel and Nexus devices.
Previous and related coverage
Google is trying to get to the bottom of a Bluetooth connectivity bug affecting Pixel and Nexus owners.
Google has hardened Android's Linux-based kernel.