Apply patch for CVE-2013-1855 in Rails 3.0.x.
user
```ruby
# Patch for CVE-2013-1855
# https://groups.google.com/forum/m/?fromgroups#!topic/rubyonrails-security/4_QHo4BqnN8
module HTML 
  class WhiteListSanitizer 
      # Sanitizes a block of css code. Used by #sanitize when it comes across a style attribute 
    def sanitize_css(style) 
      # disallow urls 
      style = style.to_s.gsub(/url\s*\(\s*[^\s)]+?\s*\)\s*/, ' ') 

      # gauntlet 
      if style !~ /\A([:,;#%.\sa-zA-Z0-9!]|\w-\w|\'[\s\w]+\'|\"[\s\w]+\"|\([\d,\s]+\))*\z/ || 
          style !~ /\A(\s*[-\w]+\s*:\s*[^:;]*(;|$)\s*)*\z/ 
        return '' 
      end 

      clean = [] 
      style.scan(/([-\w]+)\s*:\s*([^:;]*)/) do |prop,val| 
        if allowed_css_properties.include?(prop.downcase) 
          clean <<  prop + ': ' + val + ';' 
        elsif shorthand_css_properties.include?(prop.split('-')[0].downcase) 
          unless val.split().any? do |keyword| 
            !allowed_css_keywords.include?(keyword) && 
              keyword !~ /\A(#[0-9a-f]+|rgb\(\d+%?,\d*%?,?\d*%?\)?|\d{0,2}\.?\d{0,2}(cm|em|ex|in|mm|pc|pt|px|%|,|\))?)\z/ 
          end 
            clean << prop + ': ' + val + ';' 
          end 
        end 
      end 
      clean.join(' ') 
    end 
  end 
end 

```
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