The WhatsApp cloud service before late 2024 did not block certain crafted PDF content that can defeat a sandbox protection mechanism and consequently allow remote access to messaging applications by third parties, as exploited in the wild in 2024 for installation of Android malware associated with BIGPRETZEL.
https://citizenlab.ca/2025/03/a-first-look-at-paragons-proliferating-spyware-operations/