The 500px app is back in Apple's App Store after being pulled on Jan. 22 over concerns about nude imagery.
The 500px app download comes with a warning.

After Apple pulled the 500px for iOS app from its U.S. App Store on Jan. 22, the app is back today with an update that allays concerns about users finding nude imagery through the photo sharing service's app.

Version 2.0.4 adds a "Report this photo" link and comes with an age-restricted material warning when downloading it from the App Store. 

500px COO Evgeny Tchebotarev told The Verge that Apple requested the "report" functionality as well as search restrictions to prevent pornographic images from appearing in results. The new 17+ age rating is iTunes' highest, and was also an Apple requirement, according to Tchebotarev.

While Apple cracks down on 500px, the Vine video sharing app, which has been stirring up quite a bit of controversy this week as users share pornographic videos via its social network, maintains a 12+ age rating in the App Store.