Magento 2 Display error message after update 2.4.3: Invalid security or form key. Please refresh the page.
Magento 2 Display error message after update 2.4.3: Invalid security or form key. Please refresh the page. While we had this problem we were unable to export CSV table rates.
If you find the following in your system.log:
main.WARNING: Session size of 265085 exceeded allowed session max size of 256000.
The problem is the session size. To increase it, execute the following command
bin/magento config:set system/security/max_session_size_admin 512000
This will double your session size and fix your problem.
Another way to do it - using admin interface:
Store -> Configuration -> Advanced -> System -> Security -> Max Session Size in Admin