SEF makes the URLs of your Joomla website more Search Engine Friendly. And good SEF component also gives security benefits. A SEF component masks that information and makes it harder for a hacker to find eventual security vulnerabilities.
Solution:
Enable Search Engine Friendly URLs into the Joomla Administration area.
Login into Joomla Administration
Click on Site>>Global Configuration
On-Site, tab selects “Yes” next to Search Engine Friendly URLs