"In the correction, which takes the form of a letter to Sarah but the pope asks to be posted at the same websites where the cardinal's article first appeared..."

In the final paragraph of Pope Francis' letter to Cardinal Sarah, it appears to confirm that an article that was attributed to Cardinal Sarah was not, in fact, written by him.

From https://zenit.org/articles/liturgy-popes-letter-to-cardinal-sarah-unabridged-translation/

"Finally, Eminence, I confirm my fraternal gratitude for your engagement and given that the “Commentary” note was published on certain Internet sites and wrongly attributed to your person, I ask you please to do what is necessary for the divulgation of my response on those sites as well as for sending it to all the Episcopal Conferences, and to the Members and Consultors of this Dicastery."