In our paper [O] the proof of Theorem 2.7 is not correct. In that proof we constructed a space X × X and said that it had a subspace Z that was not weakly Whyburn. In fact X × X is regular and scattered, hence by Corollary 2.9 [TY] hereditarily weakly Whyburn. Thus the following problem raised in [TY] remains open: are sequential spaces hereditarily weakly Whyburn? We will now describe a Hausdorff counterexample to this problem, hence what remains open is the questions does there exist a sequential Tychonoff (or even regular) space that is not hereditarily weakly Whyburn.
