Just a few points, you'll find much more just putting "autism speaks controversy" into the search engine of your choice.

They view autism as a disease that needs to be cured.

They made videos saying autism will destroy your marriage, your family and your life.

They advocate to develop prenatal testing for autism with the goal of having women abort their supposedly autistic babies.

They treat autism as a disease to be cured, which is a disgusting way to think about it. Their founder also claimed that it's "possible" that autism is caused by vaccines, which is scientifically disproven. There are also no autistic members of their board, which means no actual representation for the people they claim to want to help.

There are a lot of reasons, but I think this article does a good job of listing the main criticisms: https://www.themarysue.com/the-autism-speaks-controversy-explained/

But in a nutshell:

• They frame autism as a disease that needs curing
• None of their board members are autistic
• They spread fear and misinformation about autism
• As a charity, embarrassingly little of their money goes to actually doing anything for autistic people

Well, donation/purchase popups are already a very big red flag in itself. Scam sites use them to drive FOMO. I have never heard of Autism Speaks so I don't know about this particular case.