What does last dot in the file permission attribute mean?

. means an SELinux ACL. (+ means a general ACL.)

Source, more info: What does the dot mean at the end of -rw-r--r--? How do you set it with chmod? on Super User

From info coreutils 'ls invocation' under Linux

GNU `ls' uses a `.' character to indicate a file with an SELinux
     security context, but no other alternate access method.

A file with any other combination of alternate access methods is
     marked with a `+' character.

Reference: The Meaning of the Dot - Stack Overflow