All adult-rated photos are considered private photos. Therefore, if a member shares private photos that are explicit, the receiver will be able to see them.
If you don’t want to see explicit photos, you can change your settings and block them:
Desktop and mobile web
Click on the three horizontal pink lines [☰] in the top-left corner;
Then on Settings;
Then Account; and
Disable View Explicit Photos.
iOS and Android
Tap on the three horizontal pink lines [☰] in the top left corner;
Then on Settings;
Then Profile Options; and
Disable Enable Rated Photos.