If you are using the new HTML based Self Service Portal for SCSM 2012 R2, then please apply this update only on the HTML portal server:
Update 3134286 is available for the System Center 2012 R2 Service Manager Self-Service Portal https://support.microsoft.com/en-us/kb/3134286
(Note: This update already contains the previous hotfix https://support.microsoft.com/en-us/kb/3124091)
Thanks
Kubilay Hüsmenoğlu