If you place stairs upside down that they form corner stairs the way as in the attachment they get a dark colour that won't go away.
MC-3620
Upside down stairs lighting bug
Resolved
Duplicate
0
Floris Kennis
(Unassigned)
Unconfirmed
lighting, stairs, upside
Minecraft 1.4.5
Retrieved
Duplicate of MC-92 , please use the search function to see if your bug has already been submitted. Currently over 30% of tickets are being closed as duplicate.