The official Ruby blog reports:

Multiple vulnerabilities in Ruby may lead to a denial of service (DoS) condition or allow execution of arbitrary code.

More discussion here and here. The community is fixing the problems energetically; but they do appear serious, and some are struggling with compatibility issues.

Since these seem to be bugs in the interpreter, it strikes me that this makes a good case for JRuby or in due course IronRuby, on the grounds that the Java and .NET runtimes are more mature. When I spoke to ThoughtWorks about its extensive Ruby work, I was told that JRuby is almost always used for deployment, partly because enterprises are more comfortable with it.