While reading the headline one can think of an analysis mechanism similar to the mempool scan invented in California, the work of Roman Matzutt, Jens Hiller and other scientists is not dedicated to it.
Instead, they chose to find out what kind of information is being shared through the coinbase data. In transactions where completely new money are being generated, one can type anything. For example, Satoshi Nakamoto, creator of Bitcoin anonymous even to this day, wrote “The Times 03/Jan/2009 Chancellor on brink of second bailout for banks” in the genesis block, probably mocking the economic state of the fiat world.
Some malevolent Bitcoin users may insert other data in the coinbase of generation transactions (which do not refer to previous ones). The German scientists behind this paper on arbitrary content found out that even the links to child pornography are being shared and try to attract attention to this completely unregulated environment.
This indicates not only a serious criminal issue, but also attracts attention to one of the oldest features of the blockchain of Bitcoin which the press often misses.