Ma'an (Arabic) reports that a series of articles being authored by longtime Arafat aide Marwan Kanafani in Egypt's Al Ahram will say that it was Yasir Arafat himself who created the Black September organization in 1970.
Black September was behind many of the highest-profile terror attacks in the early 1970s, including the murder of Jordanian Prime Minister Wasfi Tel, the Munich Olympic massacre, the May 1972 hijacking of a Belgian airliner from Vienna, dozens of letter bombs including at one that killed an Israeli politician in London, and the murder of two US diplomats in Khartoum.
The PLO always used Black September for plausible deniability, claiming that the deadliest BSO attacks had nothing to do with them. Although many historians had already made the connection between the two groups, the US State Department wrote a confidential memo in 1973 (released in 1981) showing connections between the groups, and the State Department also had linked Fatah and Arafat directly to the Khartoum murders, this appears to be the first confirmation by someone in Arafat's inner circle that it was Arafat himself who was the founder of Black September and personally in charge of operations.
And we know that the current Palestinian Arab President Mahmoud Abbas was also involved in Black September, specifically in the Munich massacre.
UPDATE: The English-language Ma'an article can be found here.