When you update to Joomla 3.6.1, it might fail with an error stating that "The most recent request was denied because it contained an Invalid Security Token."
Do not panic. According to Joomla! official website, it was due to a security fix introduced in 3.6.1. We have made a short tutorial based on the announcement made in the Joomla website
Updating from 3.6.0 to 3.6.1
This is fairly straight forward. After running the update, go to Joomla Administrator -> Extensions -> Database. Click the Fix button.
Updating from 3.5.x to 3.6.1
IMPORTANT: Take a FULL BACKUP of your site. It is better to be safe than sorry.
Step-1 : First go from your current version to Joomla! 3.6.0
For example, if you are currently using Joomla 3.5.1, you should first update to 3.6.0.
Step-2 : Update Joomla! Update Component
Before updating to Joomla! 3.6.1 from 3.6.0, you have to update Joomla! Update Component through Extension Manager.
Go to Extensions > Manage > Update
Check the Joomla! Update Component and click Update button on top left. Refer the below image
Step-3 : Update Joomla! 3.6.0 to 3.6.1
Now, you are good to updateto Joomla! 3.6.1 through Joomla! Update Component.
I have already updated from 3.6.0 to 3.6.1. What should i do?
Simple. Run the database fixer tool to delete the one file we have removed.
Go to Extensions > Manage > Database
Click on Fix button (Databse fixer tool) on top left.
More details on this issue can be found in announcement made in the Joomla website