I'm trying to add Grails extension to STS.
However when I try to find extensions at Help->Dashboard->Extensions tab I get this error:

Some sites could not be found. See the error log for more detail.
Unable to read repository at http://www.springsource.com/milestone/e3.4/site.xml.
Server returned HTTP response code: 403 for URL: http://dist.springsource.com/milesto.../e3.4/site.xml
Unable to read repository at http://www.springsource.com/snapshot/e3.4/site.xml.
Server returned HTTP response code: 403 for URL: http://dist.springsource.com/snapsho.../e3.4/site.xml

Can I somehow downoad the extension and install it manually?