Adding members to a certain secondary group

[iozay]

Is there a way I can automatically add members to a certain secondary group if they visit a page?

[bfarber]

With a plugin, of course you could. You'd do something along the lines of (untested)

\IPS\Member::loggedIn()->mgroup_others = implode( ',', array_unique( array_merge( array( X ), explode( ',', \IPS\Member::loggedIn()->mgroup_others ) ) ) );
\IPS\Member::loggedIn()->save();

Replacing X with the special group ID you want to use. Make sure to test, etc.