Find RexTarget on GitHub (MIT license).
RexTarget manipulates the target attribute of your links on Redaxo websites when you add the Redaxo variable REX_YTILS_REX_TARGET[] to your templates.
You can define the manipulation behavior in the settings.
REX_YTILS_REX_TARGET[] injects depency-free JavaScript to your web page within an anonymous function scope, so RexTarget won't cause conflicts with the rest of your code. It is recommended to add REX_YTILS_REX_TARGET[] at the end of your HTML's </body>.
Ytils RexTarget is available on the Redaxo add-on installer. Click Installer on your Redaxo backend and then find the module with they key named ytils_rex_target. You can find RexTarget on GitHub as well.