Myself, i informed the vendor about the vulnerability but they didn't agree for that so i disclosed it on exploit-db and tor :) and after a month ,they fixed it
If you want it in white hat hacker style then,
1.Inform the owner/vendor(mail them), explain them the vulnerability and they will come up with patch for the vulnerability.
2.You can publish it on CVE : https://cve.mitre.org/cve/cna.html
follow the method given in the website
black hat hacker style
1.Sell it on Tor browser
2.disclose it on exploit-db : https://www.exploit-db.com/
3.sell it on exploit hub : https://blog.exploithub.com/
4.sell it on ZDI : http://www.zerodayinitiative.com/