To remove the quarantine flag from an unnotarized QuickLook plugin – like at time of writing, QLStephen (“QLStephen.qlgenerator” can’t be opened because Apple cannot check it for malicious software.) – one can issue the following command to alleviate the issue, effectively marking the QLGenerator as safe:
xattr -cr ~/Library/QuickLook/QLStephen.qlgeneratorIf you wish to do this for all of the QLGenerators, use this:
sudo xattr -cr ~/Library/QuickLook/*.qlgeneratorIf for some reason you bump into permission problems, prefix the command with sudo like so:
sudo xattr -cr ~/Library/QuickLook/*.qlgeneratorIt is also reported that resetting quicklookd can help:
qlmanage -r
qlmanage -r cache