A tweet by user ellieeewbu today revealed that searching “brassiere” in the Photos app on iPhones categorizes photos featuring bras automatically into a group. Women have been responding to the tweet posting screenshots with similar results. Most searches show photos of lingerie, bikinis, bare skin, or in some cases, memes.

Should the fact that “brassiere” is a category at all be concerning? Or is it more alarming that most people didn’t know that image categorization was a feature at all?

Image recognition was introduced with iOS 10 in June 2016, when the Photos app was updated with deep learning for object and scene detection. Apple stressed during the keynote, as well as on its website, that all object detection is done completely locally on the device.

In a Medium post, developer Kenny Yin detailed all of the facial expressions and objects the Photos app recognized, which he found through a few lines of code in the framework of macOS Sierra’s Photos app. At the time it was released, the app was capable of recognizing seven different facial expressions, and a total of 4,432 keywords, “brassiere” included. You can read the full list here.

One thing to note here is that while women’s undergarments like “bra” are listed as categories, there’s no mention of men’s boxers or briefs. Clearly someone had to have made a conscious decision to include (or not include) certain categories. Even “corset” and “girdle” are on the list. Where is the same attention to detail for mens’ clothing?

Despite the fact that this categorization has been around for over a year, there’s something to be said about users just finding out about it now. Considering that machine learning image recognition was hyped as a prominent Google Photos feature since May 2015, I was surprised to find out that the Photos app on my iPhone had the same feature. Most people know about the facial recognition and Memories features on their phones, but based on the reactions from today, it’s likely that many people (myself included) now know just how specific the image categories can get.

For the record, Google Photos does the exact same thing when you search “brassiere,” except your photos are stored on the cloud, in Google’s servers. If anything, this should be the bigger security concern that’s freaking out people on Twitter.