Forthright and Upfront

Forthright adjective - Free in expressing one's true feelings and opinions.

Upfront and forthright are semantically related in outspoken topic. In some cases you can use "Upfront" instead an adjective "Forthright", when it comes to topics like straight from the shoulder. informal substitute

Upfront adjective - Frank and honest.

Forthright and upfront are semantically related in open topic. You can use "Forthright" instead an adjective "Upfront", if it concerns topics such as truthful, straightforward.