What is a word for "to take pleasure in someone else's success"?

This appears to be similar to this question, What's the antonym for Schadenfreude?

With the two most up-voted answers being Mitgefühl (a German word for "compassion") and Mudita (a Buddhist term for "finding joy in the happiness and success of others").

It is possible that you are vicariously happy. Something that is vicarious is, according to Merriam-Webster,

experienced or felt by watching, hearing about, or reading about someone else rather than by doing something yourself.

So, to be vicariously happy is to be happy for someone else's achievement as though it were your own.