But Edinburgh centre Phil Burleigh has been cleared of making contact with the eye of an opponent during the same game at the RDS.
McFadden, who scored two tries in the match, looked fortunate to avoid a yellow card at the very least for his challenge.
However, he was subsequently cited and his case was dealt with yesterday by an independent Pro12 Rugby Disciplinary Committee in Cardiff.
The winger denied foul play but after viewing video footage and listening to representations from and on behalf of the player, the all-Welsh committee found McFadden guilty of “an act of foul play, by recklessly carrying out a high and dangerous tackle”.
The committee, chaired by Simon Thomas, alongside Owain James and Roger Morris, determined that the tackle merited a lower-end entry point based on World Rugby’s scale of seriousness, which carries a two-week playing suspension. But they added a further week as “a deterrence to combat a pattern of offending”.
McFadden, who can appeal, is now banned until 22 May, taking into account the weeks in which he was not expected to play.
Burleigh, meanwhile, appeared before the same committee, having also been cited by an independent citing commissioner.
The Edinburgh centre denied foul play and the committee agreed, meaning Burleigh is available for Edinburgh’s next match, against Munster away a week on Friday.
A statement issued last night by the Guinness Pro12 said: “On the balance of probabilities, Mr Burleigh had not committed an act of foul play as alleged. Accordingly the Disciplinary Committee did not uphold the citing and Mr Burleigh is free to resume playing immediately.”