In Redcarpet before version 3.5.1, there is an injection vulnerability which can enable a cross-site scripting attack.
In affected versions, no HTML escaping was being performed when
processing quotes. This applies even when the
option was being used.
For Debian 8 jessie, these problems have been fixed in version 3.1.2-1+deb8u1.
We recommend that you upgrade your ruby-redcarpet packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/