I hate people who make post that say "Oh yeah, I got the goods but I can't tell YOU." That's much like what 8 year olds do.
Seems to me if they really had concerns about a security issue, it would be best to not say anything at all.
She has shared some things about her sis before...so it seems natural to further expound a little. If she hadn't been a regular, and if we didn't know anything about her..I can see where you are coming from.