Is There Corruption in Buddhism?
Yes. Sadly, it is human nature. Corruption is found in all major religions due to delusion or greed or anger.
Those spreading the words of the original spiritual teachers can end up misrepresenting/corrupting their teachings.
When the Buddha arrived to teach in Kesaputta, the town of the Kalamas, the people there questioned the Buddha about his teachings. They told him that many different teachers had been to their town teaching different doctrines. Each praised their own teachings and disparaged the teachings of others. The people asked the Buddha, "How do we know who to believe? How do we know who is speaking the truth?"
The Buddha told them to not believe teachers just because they talk well or come from a known lineage or because people say good things about them. Instead, the Buddha told the Kalamas to consider whether or not following a teaching leads to harm and suffering. If it leads to harm and suffering it is unwholesome and blameworthy and should be abandoned.
Greed is an unwholesome condition as is hatred and delusion. These three states all lead to harm and suffering. They are unwholesome and blameworthy. Others don't have to tell us this. We know it for ourselves that greed, hatred and delusion lead to harm and suffering and are therefore unwholesome and blameworthy.
On the other hand, teachings that lead to non-greed, non-hatred and non-delusion lead to the welfare and happiness of ourselves and others. These teachings are wholesome and blameless.
Teachers who teach generosity, kindness, compassion, mindfulness and peacefulness which lead to stillness and wisdom, these are the ones that we can feel confident are teaching the truth.