AcyMailing is a reliable Newsletter and email marketing extension for
Joomla.
It enables you to efficiently manage an unlimited number of subscribers,
organize them into mailing lists, send personalized newsletters (Hi
{name}...)
2. Technical Description:
CSV Injection (aka Excel Macro Injection or Formula Injection) exists in
the export feature in the Acyba AcyMailing extension before 5.9.6 for
Joomla! via a value that is mishandled in a CSV export.
3. Proof Of Concept:
Login as low privileged user who is having access to Acymailing Component.
Rename user name as @SUM(1+1)*cmd|' /C calc'!A0.
When high privileged user logged in and exported user data then the CSV
Formula gets executed and calculator will get popped in his machine.
4. Solution:
Upgrade to version 5.9.6
https://extensions.joomla.org/extension/acymailing-starter/