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Last tested: May 11, 2020
Starting in Looker 7.8 (and backport patches for 7.4 and 7.6), "string" type User Attributes will no longer support the "%" wildcard character in group or user values. Any "%" characters in a "string" type User Attribute's group or user values will be treated as regular, non wildcard characters. Note, this may impact the results of queries using such User Attributes in filters (specifically access_filters), as the "%" character will go from "matches anything" to "equals '%'". If "%" wildcard characters are needed in string-based User Attributes, please use the "string (advanced)" type as our docs recommend.