If i read it all correctly i don't think this latest one really affects us.
Because it is related to MDC lookups, and to be clear yes Servoy does use them this is our default pattern:
<PatternLayout pattern="%d %p [%t] %c - %m [$${servoy:clientid:-} $${servoy:solution:-}]%n" />
But those 2 are not user defined inputs a user can't set the values of that by there own thing. These are all fixed servoy controlled values.
There is maybe a possible scenario where a user could influence the output because we also add this, if it is set, to MDC: if (username != null) MDC.put("username", username);
so if a user makes a username with a jndi lookup string and the pattern will expand that, which we don't do by default in our pattern, so the pattern doesn't have $${servoy:username:-} but i think if that is added it could potentially do a lookup