One of our heavy-used Wicket production applications has developed 'interesting' behaviour since upgrading to 7.9.0: after a while the system becomes slower and seems to need more CPU time to handle the same amount of requests. Threaddumps exposed that a lot of CPU time was consumed by java.lang.ThreadLocal$ThreadLocalMap.getEntryAfterMiss, pointing to a ThreadLocal leak.
After making a heapdump (20g) of one of our servers we found lots of ThreadLocalMap$Entry objects referenced by org.apache.wicket.page.PageStoreManager$SessionEntry$1 containing the value Boolean.FALSE.
Seems that boolean is new behaviour introduced by the fix for
WICKET-6465 and is causing complications on servers like Wildfly we use which don't recycle threads.