Short answer: It’s on StarWars.com.
Long answer: It’s on StarWars.com, and is reported by media outlets as such. The outlet will either source/link StarWars.com or have quotes from Lucasfilm people using their actual names.
For a recent example of an outlet actually breaking news with Lucasfilm’s blessing, let’s look at IGN’s original report of David Tennant in The Clone Wars. It has extensive quotes from Dave Filoni and a video clip – which was exclusive to them when the story broke. (StarWars.com later posted it as a preview of the episode.) So far, Lucasfilm hasn’t been doing this with Episode VII news – the Arndt item simply appeared on the site – perhaps because they know that everyone is going to write about it anyway. The Tennant news simply isn’t as big, and getting it onto a mainstream outlet gives it an extra boost that will reach casual fans (and people like Doctor Who fans) who aren’t regularly watching The Clone Wars. This is also probably why Del Rey gave Entertainment Weekly that Scoundrels exclusive EU fandom spent a day agonizing over back in March.
Other outlets writing about those stories does not confirm them, either. Words like ‘reports’ and ‘reportedly’ are basically just a journalistic way of saying ‘rumors.’ It might give them a little more weight – I tend to use the word ‘report’ if I think something is just a tad more plausible than things like, say, Vader rising from the dead. But in essence? They mean exactly the same thing: It’s not official yet, just things people or the media are saying. That doesn’t make them fact, no matter how many people run the story.
Because nothing is confirmed until Lucasfilm says it is. Lucasfilm and, now, Disney. Not Major Entertainment News Outlet #47 reporting off Major Entertainment News Outlet #86. And trust me, we are watching.