The German photographer Robert Kneschke found out in February that his photographs were being used to train AI through LAION-5B, which is a dataset of over 5.8 billion images owned by the non-profit Large-scale Artificial Intelligence Open Network (LAION) that has been used by companies like Stability AI.
Here is the photographer’s blog post (in German): https://www.alltageinesfotoproduzenten.de/2023/04/24/laion-e-v-macht-ernst-schadensersatzforderung-an-urheber-fuer-ki-trainingsdaten/
Someone set up HaveIBeenTrained.com to check this: For any of it’s faults, the LAION people have been very transparent on their sources of training data, their whole dataset is available. So, you can check if your stuff is inside it.