When a pre tag is used in spoilers (as the 4-space code block doesn't work), the standard gray pre/code background is not hidden when the spoiler is, but the text color within is set to the spoiler block background. The result is that the text within is actually visible while the spoiler is hidden.
HiddenSee what I mean?Text
Either the whole pre block should be hidden or the text within should be made the same color as its immediate (gray) background.
Observed on several different sites in Safari, Chrome, and Firefox on OSX Yosemite.