Magento 2.4.3 Session Size Error
After upgrading to Magento 2.4.3 you may see the above error after creating a new order or trying to add a new product in the admin panel. After checking the logs you’ll see a message similar to:
“Session size of xxxxxx exceeded allowed session max size of 256000”
After slamming your head on the table or wall for a few minutes, hopefully you will stumble across this post and it will help. The simple fix for this is to just run the following command:
bin/magento config:set system/security/max_session_size_admin 0
Then just flush your cache:
Simple as that. I hope this helps!