Wasalam
May Allah bless you.
If the share is halal and the transaction is in line with the correct shariah paramètres, then it is permissible to buy the shares.
However, morally it is wrong to take part in this sort of market manipulation. Under an Islamic system, the leader of the Muslims could even stop this type of behaviour.
If it is proven that such action causes harm to people, then it can even be considered as haram.
And Allah knows best!