We recommend that you review Post-installation Messages immediately after updating the Joomla! CMS.
If there are any NEW messages after you update your website's Joomla! CMS then you will see a BELL (see image) at the top of the website Dashboard.
You will also see a YELLOW BOX displayed next to Installation Messages in the System Dashboard screen.
Messages should not be hidden until you have read them.
And SECURITY messages should NEVER be ignored.
Once you have dealt with messages they can however be hidden away.
Show Hidden Messages
If later you want to read hidden messages, you can.
Example Messages which impact on SECURITY
Did you update a website using an older version of Joomla! CMS but ignored these messages?
If YES then re-read and act on the messages shown below.
Need help, just ask.
Post Joomla! 3.9.22 Bug Fix Release
Post Joomla! 3.9.21 Security Fix Release
Post Joomla! 3.9.19 Security Fix Release
Post Joomla! 3.9.3 Security Fix Release
Post Joomla! 3.8.8 Security Fix Release