Galaxy Z Fold 4 became the first Galaxy device to receive the January 2024 security patch. The new firmware version is F936BXXS4EWL5 and it comes in 411MB file size. As per the changelog, Samsung has improved its security and fixed the bug to enhance the overall experience. At the moment, we are not sure which bugs & vulnerabilities have been taken care of, so wait for the official post.
The other foldable Galaxy Z Flip 4 is supposed to get the January 2024 security patch today, though you can check for it. For Galaxy Fold 4, the update is now rolling out in Europe. This week, Galaxy S23, Fold 5, and Flip 5 might get the same treatment from the company. To install the January patch, open Settings on your foldable phone, then go to Software Update, and here click on Download & install.