A software-properties security update has been released for Debian GNU/Linux 9 LTS to address an issue where an ansi escape sequence can be injection into software-properties.

DLA 2339-1: software-properties security update

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Debian LTS Advisory DLA-2339-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/
August 22, 2020   https://wiki.debian.org/LTS
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Package : software-properties
Version : 0.96.20.2-1+deb9u1
CVE ID : CVE-2020-15709
Debian Bug : 968850

Jason A. Donenfeld found an ansi escape sequence injection into
software-properties, a manager for apt repository sources. An attacker
could manipulate the screen of a user prompted to install an
additional repository (PPA).

For Debian 9 stretch, this problem has been fixed in version
0.96.20.2-1+deb9u1.

We recommend that you upgrade your software-properties packages.

For the detailed security status of software-properties please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/software-properties

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