This code:
[[Image:Old ladder inside Carlsbad Cavern-57.JPG|thumb|Old ladder inside a [[cave]]]]
Is not showing any image. However, this one works:
[[Image:Old ladder inside Carlsbad Cavern-57.JPG|thumb|180px|Old ladder inside a [[cave]]]]
It was first brought to my attention on Simple Enlglish Wikipedia but is not limitted to that wiki. I haven't found any other image which breaks like this. As there are possibly many cases where "thumb" command is used without a size definition, I am marking this bug as major.
Version: unspecified
Severity: major