/System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/2.0.0/universal-darwin13/rbconfig.rb:213: warning: Insecure world writable dir /usr in PATH, mode 0
Executing the following worked for me on Mac OS X 10.11 El Capitan
sudo chmod o-w /usr/local
The error occured when loading a vagrant as follows;
vagrant status
/opt/vagrant/embedded/gems/gems/vagrant-1.8.1/lib/vagrant/pre-rubygems.rb:31: warning: Insecure world writable dir /usr/local in PATH, mode 040777
/opt/vagrant/embedded/gems/gems/bundler-1.10.6/lib/bundler/shared_helpers.rb:78: warning: Insecure world writable dir /usr/local in PATH, mode 040777
ls -dal /usr/local/
drwxrwxrwx 10 root wheel 340 Sep 9 15:05 /usr/local/
After running the chmod mentioned above.
ls -dal /usr/local/
drwxrwxr-x 10 root wheel 340 Sep 9 15:05 /usr/local/
Which solved the problem.