Anytime a learned biblical scholar writes about his or her conjectures, there are plenty of other scholars whose conjectures are directly opposed to them.I have, as have MANY more qualified actual scholars.
The preponderance of evidence is clear about what Paul wrote.
Dictionary of Paul & His Letters by G.F. Hawthorne, R.P. Martin & D.G. Reid, eds.
But the evidence of some of Paul's letters not actually written by him is pretty well established today.
People who know one or more ancient languages and study textual coherence can tell when a section of or the entirety of a book is not from the original author. Its style and vocabulary are different and the theology might undergo a major change.