It's a good question, but it brings up a point --
I think the Church used to rely on the Faithful having a bit of common sense.
Did the Church have to release a specific encyclical against each of 1000 forms of sin against the Sixth and Ninth: porn novels, porn magazines, "gentleman's clubs", and 50 other occasions of sin? Or do they content themselves with prohibitions against "occasions of sin" and leave the application to common sense?
And for those with no common sense, and/or the IQ of a gerbil, then the fallback "ask your priest" should suffice to cover it.
I bet you can't find a single Church docuмent or prohibition against porn websites, for example -- unless you cite something general and vague. Which is fine, and as it should be. The Church can't be expected to spell out every specific sin.
For example, we can rely on the Golden Rule. If you wouldn't like your wife going out to dinner with a strange man, then YOU shouldn't be that strange man going out to dinner with another man's wife.
If you wouldn't want some sleazebag doing such-and-such to your wife, then you shouldn't do those things with another woman. And so on.