The following WebCenter Portal 12c Bundle Patch (22.214.171.124.190416) was released on April 16, 2019. Note that this Bundle Patch 126.96.36.199.190416 must be installed with the latest WebCenter Core Bundle Patch 188.8.131.52.180910 (also available for download below in case you don't already have it installed).
Bug 29510069 - webcenter portal bundle patch 184.108.40.206.190416 (Doc ID 29510069.8)
Bug 28633811 - webcenter core bundle patch 220.127.116.11.180910(id:180910.2130.s) (Doc ID 28633811.8)
Recommended Patches for Oracle WebCenter Portal (Doc ID 1087226.1)
At this time, there are no plans for another WebCenter Portal 18.104.22.168.x Bundle Patch release.