Zaid Alsalami, Shaykh Dr Zaid Alsalami is an Iraqi born scholar, raised in Australia. He obtained a BA from Al-Mustafa University, Qom, and an MA from the Islamic College in London. He also obtained a PhD from... Answered 3 years ago
Bismihi ta'ala
It could even be obligatory to inform the friend about what you know about the person. Of course, you must make sure your information is accurate, and also it somehow does not backfire onto you.
It would not be considered as gheebah.
I would just advice it be done in a very diplomatic way, so as to avoid any problems from any side.
And Allah knows best.