I came across this news piece today about a document that the Congregation for the Doctrine of the Faith has published on the subject of apparitions and private revelation. The document dates back to 1978 but it has not been "officially" released to the public until now. (Hmm, we wonder! Why now?) I think that it has had public access throughout these years, but there is something about it now being "officially" released.
If you have a chance to read, above is the short news release. Pay attention to the second-to-last paragraph which briefly explains that official approval of a private revelation only means that there has not been anything found about the event that speaks contrary to the Church's teaching.
Here is a version of the document from the CDF that I found on the Vatican's website.
Note that "private revelation" is not the same as "public revelation." Private refers to an individual or group's experience, while public revelation refers to Jesus himself, his teachings, and the work of the first apostles in the early Church. Basically, public revelation is the New Testament. Public revelation is to be believed by all the faithful but private is only binding on the individual that receives it.