A php-horde-text-filter security update has been released for Debian GNU/Linux 9 LTS to address a cross-site scripting (XSS) vulnerability.

DLA 2564-1: php-horde-text-filter security update

- -----------------------------------------------------------------------
Debian LTS Advisory DLA-2564-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Sylvain Beucler
February 18, 2021   https://wiki.debian.org/LTS
- -----------------------------------------------------------------------

Package : php-horde-text-filter
Version : 2.3.5-1+deb9u1
CVE ID : CVE-2021-26929
Debian Bug : 982769

Alex Birnberg discovered a cross-site scripting (XSS) vulnerability in
the Horde Application Framework, more precisely its Text Filter API.
An attacker could take control of a user's mailbox by sending a
crafted e-mail.

CVE-2021-26929

An XSS issue was discovered in Horde Groupware Webmail Edition
(where the Horde_Text_Filter library is used). The attacker can
send a plain text e-mail message, with JavaScript encoded as a
link or email that is mishandled by preProcess in Text2html.php,
because bespoke use of \x00\x00\x00 and \x01\x01\x01 interferes
with XSS defenses.

For Debian 9 stretch, this problem has been fixed in version
2.3.5-1+deb9u1.

We recommend that you upgrade your php-horde-text-filter packages.

For the detailed security status of php-horde-text-filter please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/php-horde-text-filter

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://wiki.debian.org/LTS