This is old news- this was discovered 6 years ago. This 'new study' is just rehashing things that are already known.
**First, this is hashed data (so you need special tools to view it, assuming you download a copy of the entire blockchain, and could even locate the blocks).
**Second, the arbitrary (i.e. non-transactional) data is capped at around 100bytes.
**Third, this is just URLs leading to (mostly long ago taken offline) darknet sites, not even visitable from a regular browser (you'd need something like Tor).
**Fourth, very few users of BTC host the full blockchain.
So, while it is less than ideal, it is old news, and not 1/1,000 as bad as the media is portraying it to be. They make it sound like there are child abuse images all over the blockchain.
It sucks, but is generally pure FUD-mongering.
RE: Bitcoin also gives you Child porn or just FUD?