Seems that since the update, on occasion new builds/prims rezzed are default to FULL PERMS. Meaning, unless you change the permissions before you sell it or give it away, it will arrive in the other person's possession FULL PERMS -- yikes.
I first noticed it Thursday night while I was building and putting together a new avatar, and when I went to modify a stack of the components, I noticed that on the prim pieces, all 3 permissions boxes were checked. I changed it and didn't think too much of it until today...
I went out to buy something from a shop that I had just read about in classifieds, and half of the items in the folder were at full perms. I warned the owner about it (needless to say, she kinda freaked out), and now I'm passing the word along here as well.
I tested it again just now and it hasn't done that again, so the bug may be sporadic, who knows. Just make sure you double, triple check everything before selling or giving away stuff. :\