ID:1980514
 
Resolved
Data attributes were not usable in a custom .dms skin.
BYOND Version:509.1313
Operating System:Windows 10 Pro 64-bit
Web Browser:Chrome 46.0.2490.80
Applies to:Webclient
Status: Resolved (509.1314)

This issue has been resolved.
Descriptive Problem Summary:
Removing disallowed attribute <BUTTON data-toggle="dropdown">

Why?
I'll add data attributes into the whitelist for the webclient's filter.
Lummox JR resolved issue with message:
Data attributes were not usable in a custom .dms skin.
Is there a workaround I can put in place in webclient.dart.js or something so I don't have to wait for the next version? I need to use data-toggle so I can get Bootstrap's dropdown functionality to work (among other things).
No easy workaround yet, no. The easiest thing would be for your own script to wait for the DOM to load and apply the attribute then.