If and I say IF a reporter (legit or otherwise) approached a juror, that probably wouldn't be grounds for a mistrial but they'd have to have a hearing with the juror about the details of the encounter and if the juror felt swayed. At worst that juror might be excused.
NOTE: I'm not an attorney, but this is what I believe to be true.
In the Charles Manson case, back in 1971 or so, Manson himself held up a newspaper with a banner headline "Nixon thinks Manson Guilty". There was no mistrail, but each juror had to be questioned if they felt swayed.
One guy said, "no, I didn't even vote for Nixon".