A lxml security update has been released for Ubuntu Linux 16.04 LTS, 18.04 LTS, 20.04 LTS, and 20.10.

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Ubuntu Security Notice USN-4896-1
March 30, 2021

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

- Ubuntu 20.10
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

lxml could allow cross-site scripting (XSS) attacks.

Software Description:
- lxml: pythonic binding for the libxml2 and libxslt libraries

Details:

It was discovered that lxml incorrectly handled certain HTML attributes. A
remote attacker could possibly use this issue to perform cross-site
scripting (XSS) attacks.

Update instructions:

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

Ubuntu 20.10:
python3-lxml 4.5.2-1ubuntu0.4

Ubuntu 20.04 LTS:
python-lxml 4.5.0-1ubuntu0.3
python3-lxml 4.5.0-1ubuntu0.3

Ubuntu 18.04 LTS:
python-lxml 4.2.1-1ubuntu0.4
python3-lxml 4.2.1-1ubuntu0.4

Ubuntu 16.04 LTS:
python-lxml 3.5.0-1ubuntu0.4
python3-lxml 3.5.0-1ubuntu0.4

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

References:
  https://ubuntu.com/security/notices/USN-4896-1
CVE-2021-28957

Package Information:
  https://launchpad.net/ubuntu/+source/lxml/4.5.2-1ubuntu0.4
  https://launchpad.net/ubuntu/+source/lxml/4.5.0-1ubuntu0.3
  https://launchpad.net/ubuntu/+source/lxml/4.2.1-1ubuntu0.4
  https://launchpad.net/ubuntu/+source/lxml/3.5.0-1ubuntu0.4