rubygems-pwn: A Vulnerability in RubyGems (currently being fixed)
If you’ve seen people saying to run
gem install rubygems-pwn on Twitter (which I don’t advise!), it’s because it’s a proof of concept for a vulnerabilty in RubyGems. The rubygems-pwn project on GitHub has more information about it, but essentially you can push arbitrary Ruby code into gemspec parameters which will then be executed later on. The vulnerability has been discussed in the rubygems repo where a fix has already been made but, hopefully, more general fixes should be made available soon. (If you want to see the direct example of a malicious gemspec, look here.)
Update: RubyGems 1.8.10 has been released to address this vulnerability.