Several security issues were fixed in Libxslt.

==========================================================================
Ubuntu Security Notice USN-4164-1
October 22, 2019

libxslt vulnerabilities
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 19.10
- Ubuntu 19.04
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 ESM
- Ubuntu 12.04 ESM

Summary:

Several security issues were fixed in Libxslt.

Software Description:
- libxslt: XSLT processing library

Details:

It was discovered that Libxslt incorrectly handled certain documents.
An attacker could possibly use this issue to access sensitive information.
This issue not affected Ubuntu 19.10. (CVE-2019-13117, CVE-2019-13118)

It was discovered that Libxslt incorrectly handled certain documents.
An attacker could possibly use this issue to execute arbitrary code.
(CVE-2019-18197)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 19.10:
  libxslt1.1                      1.1.33-0ubuntu1.1

Ubuntu 19.04:
  libxslt1.1                      1.1.32-2ubuntu0.2

Ubuntu 18.04 LTS:
  libxslt1.1                      1.1.29-5ubuntu0.2

Ubuntu 16.04 LTS:
  libxslt1.1                      1.1.28-2.1ubuntu0.3

Ubuntu 14.04 ESM:
  libxslt1.1                      1.1.28-2ubuntu0.2+esm1

Ubuntu 12.04 ESM:
  libxslt1.1                      1.1.26-8ubuntu1.6

In general, a standard system update will make all the necessary changes.
make all the necessary changes.

References:
  https://usn.ubuntu.com/4164-1
  CVE-2019-13117, CVE-2019-13118, CVE-2019-18197

Package Information:
  https://launchpad.net/ubuntu/+source/libxslt/1.1.33-0ubuntu1.1
  https://launchpad.net/ubuntu/+source/libxslt/1.1.32-2ubuntu0.2
  https://launchpad.net/ubuntu/+source/libxslt/1.1.29-5ubuntu0.2
  https://launchpad.net/ubuntu/+source/libxslt/1.1.28-2.1ubuntu0.3