It was discovered that there was a authentication bypass vulnerability in libxslt, a widely-used library for transforming files from XML to other arbitrary format.
This vulnerability was caused by invalid handling of xsltCheckRead and xsltCheckWrite -1 error return value, handled as a success code. Remote attackers could leverage this vulnerability to bypass protection mechanisms and possibly cause unauthorized disclosure of information or modification.
For Debian 7 Wheezy, these problems have been fixed in version 1.1.26-14.1+deb7u4.
We recommend that you upgrade your libxslt packages.
Further information about Extended LTS security advisories can be found at: https://deb.freexian.com/extended-lts/