If you had read the article, you'd have seen that Fellay is one of the five still-in-office bishops who are accused by the French tv programme of involvement in these abuse cases.
To know more, you might try to see the programme in full; or read the related book (which is mentioned in this article); or do some simple online-searching?
I've tried the third of these options. Two minutes' searching brought up the case of "le père P", who looks to be an SSPX alleged offender. You might wish to do some more thorough online-searching than me, if you're interested in Fellay and the SSPX?