There is a problem with hidden abusefilters, for example: this filter is actually not hidden: https://de.wikipedia.org/wiki/Spezial:Missbrauchsfilter/3, but older versions are hidden, for example, the last hidden version: https://de.wikipedia.org/wiki/Spezial:Missbrauchsfilter/history/3/item/40, without sysop rights not visible. The version after this is not hidden, so visible for all users: https://de.wikipedia.org/wiki/Spezial:Missbrauchsfilter/history/3/item/42. The problem now is, that the difference is visible for all users: https://de.wikipedia.org/wiki/Spezial:Missbrauchsfilter/history/3/diff/prev/42, and also the difference beetween hidden versions: https://de.wikipedia.org/wiki/Spezial:Missbrauchsfilter/history/3/diff/prev/40, so non sysops can construct the hidden version, thats the problem.