1.Browse through your target.
2.Find a article or blog present on target website which must have a link to share that blog on different social networks such as
3.Let's say we got and article with url:
then just appened it with payload ?&u=https://attacker.com/vaya&text=another_site:https://attacker.com/vaya
4.Now hit enter with the abover url and just click on share with social media.
Just observe the content if it is including our payload i.e. https://attacker.com
Then it is vulnerable or else try next target.