The page, posing as an activist group, was one of hundreds of fake accounts Russia used in an information campaign during the election, a revelation that has put Facebook on the defensive.
The regret is one of a catalog of mistakes — large and small — that Mrs. Clinton lists in the election post-mortem “What Happened.”
Posing as ordinary Americans on Facebook and building “warlists” of Twitter accounts, suspected Russian agents infiltrated last year’s election.
A Times investigation has found that infiltration efforts were broader than previously disclosed and that state and federal agencies have conducted few forensic inquiries.
President Trump charged that James B. Comey had “exonerated” his opponent Hillary Clinton before completing an investigation.