Crass is a Ruby CSS parser that's fully compliant with the CSS Syntax Level 3 specification. Prior to 1.0.7, when Crass parses input containing `non-ASCII characters`, inefficiencies in tracking the positions of `multi-byte characters` result in superlinear parsing time. An attacker-controlled CSS input consisting of many `non-ASCII characters` can therefore cause excessive CPU consumption and potentially denial of service. This issue is fixed in version 1.0.7.