The first relates to communal celebrations of the Sacrament of Penance (Rite 2). Rite 2 involves a communal celebration, perhaps including a form of examination of conscience. The opportunity for individual confession is then available. In this context Fr John writes, citing the Sacred Congregation for Divine Worship, that these individual confessions should be integral confessions, and not simply occasions where the faithful mention just one sin.
"Neither is it acceptable for children or adults to be told that they need only confess one sin."
My own view, given the juridical nature of the Sacrament of Penance and the clear direction from the relevant Sacred Congregation, is that a "one sin only" confession will give rise to an absolution that is at best doubtful and, in all probability, invalid. [Comments please if your expertise is greater than mine and you disagree...]. It is certainly unlawful.
The second abuse that Fr John refers to is that of washing the feet of women during the Thursday evening Mass of the Lord's Supper. The rubric of the Roman Missal (Ordinary Form) is very clear that it is only men that should be chosen to have their feet washed.
See Fr John's post "Liturgical abuses at Easter Time" at http://south-ashford-priest.blogspot.com/ for more details.