Hi,

do you mean that query string value is always different or query string itself?

In the first case is solution simple. For example if the landing URL is:

http://<domain>/examples/web-parts/general/actions/random-redirection.aspx?test=myquey

In property of web part you can configure for example:

~/home.aspx?test={%test|(default)something%}

In case you need to read whole query string part you can create for example a custom macro which will work with URLHelper class and returns a query section.

Best regards,
Ivana Tomanickova