Summary: Under certain conditions a user who accesses a workbook as a Guest user can view data as the publisher of the data.
Vulnerable Versions: Tableau Server 9.0.0 (through 9.0.2)
Resolution: The issue can be fixed by upgrading to the following Tableau Server versions:
Tableau Server 9.0.3
Work around: In the meantime, disable Guest access.
Knowledgebase Article: Security Advisory: Guest Users Can See Data As the Publisher User | Tableau Software