Under 10.12.6 running Safari 11.0.3 (12604.5.6.1.1), no file named WBSAutoFillQuirks.plist exists anywhere on the file system. The closest named file I found is

Under 10.12.6 running Safari 11.0.3 (12604.5.6.1.1), no file named WBSAutoFillQuirks.plist exists anywhere on the file system. The closest named file I found is WBSPasswordGenerationRequirementsByDomain.plist which is found under /System/Library/StagedFrameworks/Safari/SafariShared.framework/Versions/A/Resources/ I've posted its contents here - https://pastebin.com/iPY6gLSC https://pastebin.com/iPY6gLSC There's a separately named WBSFormAutoFillKeywords.plist.