ruby2.7 regression

USN-7256-1 fixed vulnerabilities in Ruby. The update introduced a minor
regression. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

It was discovered that Ruby incorrectly handled parsing of an XML document
that has specific XML characters in an attribute value using REXML gem. An
attacker could use this issue to cause Ruby to crash, resulting in a
denial of service.