The Linux file permissions for version 3.0.0 are incorrectly set in the download archive files. The correct file permissions should be read/write only for the owner and read-only for group and other. In the 3.0.0 archives, this is incorrectly set as read-write for the owner and group members.
For example, if you do the command
ls -l at the Joomla root folder, you will see:
-rw-rw-r-- ..... joomla.xml
Instead you should see:
-rw-r--r-- ..... joomla.xml.
You can fix this from the Linux command line by navigating to the root folder of Joomla and typing this command:
chmod -R g-w *
Note: This will be corrected automatically when you update to version 3.0.1.