Instagram is developing a feature that would allow users to control their exposure to possibly offensive and harmful content. This is a filter that can turned on and off at any moment. You can see how it looks according to the last available sources here:
When turned on, the filter will make sure that the user sees less sensitive content. Some users have reported that it was on already when they discovered it.
It looks like this new update is still at the testing stage, so we have to wait and see how it will look in the end and whether it will be officially rolled out.