I didn't think this was possible, however, i found this quote:

It is strongly discouraged to use both allow-scripts and allow-same-origin at the same time, as that allows the embedded document to programmatically remove the sandbox attribute.

My iframe needs to have a sandbox, but only when I am browsing in certain URLs where the embedded browsing context tries to navigate (load) content to the top-level browsing context (Jump out of frame...)

On other pages the sandbox needs to be removed entirely, as it wont allow me to browse away from a site with a different origin...

The frame attempting navigation is sandboxed, and is therefore disallowed from navigating its ancestors.

Programatically changing the sandbox with :

document.getElementById(frame).sandbox = ;

...doesnt work either as this still places restrictions... Therefore, i need to somehow remove the attribute entirely, how would i go about doing this?