The source article is linked to on the story, and it says screenshots were taken. My parsing interprets it as saying that they showed these screenshots to security researchers.
“screenshots were shared with de Volkskrant by the monthly opinion magazine Vrij Nederland. Dutch security experts find Gevers’ claim credible.”
Also, the guy has a history (well, both do). Gevers has got into numerous other accounts before, and uncovered some disturbing stuff - tracking of Chinese Muslims via facial recognition stuff in China for example.
