Since the whitelist process is list-of-strings oriented, it will reject custom `data-*` attributes that are being used. The hack to change it is described here: https://github.com/rubys/venus/pull/19/files#diff-dcd60d82836175427dfbdf792aa976ecL172 I'm fairly certain that `data-*` is "safe" so it seems like there should be some way to keep it. BTW: I looked and looked to see if this issue was already discussed somewhere (given the above link, I figured it would be) but I couldn't find it.