After patching Ubuntu and Firefox ESR (2017/6/21) the Java Plugin suddenly started to crash. The Linux Kernel was patched the day before the the machine was not rebooted. After installing latest patches, rebooting and an update of Firefox ESR this problem started. I have tried to empty the browser and Java Plugin caches. I have also tried to enable the plugin console and logging but nothing indicating a crash is logged to ~/.java/deployment/log.