Word for a person who freely shares others' secrets [closed]

"gossiper" fits perfectly. (not specific for secrets, though)

• a person given to gossiping and divulging personal information about others - TFD

"yenta" is a slang word for a person, especially a woman, who is considered to be meddlesome or gossipy.

• a person who habitually reveals personal or sensational facts about others. e.g. "the couple's loud quarrel had the building's yentas yapping for a week." MW

related words: blab, gossip, gossipmonger, newsmonger, rumormonger, scandalmonger, tabby, talebearer, taleteller, tattle, tattler, tattletale, telltale, whisperer.

A blabbermouth, perhaps

('blab' - to talk much or ineptly; to chatter, babble, ‘blether' (OED))

indiscreet

saying or doing things that tell people things that should be secret or that embarrass people:
In an indiscreet moment, the president let his genuine opinions be known.
They have been rather indiscreet about their affair. — cambridge.org