Certain blocks which should only emit light from a specific face actually emit light from all of their faces. In snapshot 12w39a a change was made to correct this and only make them emit light from the intended faces, but was reverted, and the change was not reimplemented with the 18w43a lighting fixes. In the provided screenshots the blocks in question should only be emitting light from their front face, but can be seen emitting light from their top face.

Affected blocks:

• minecraft:jack_o_lantern
• minecraft:furnace (when lit)
• minecraft:blast_furnace (when lit)
• minecraft:smoker (when lit)
• minecraft:lava_cauldron