Removal of JndiLookup in now obsolete Minecraft versions, or versions that still have log4j < 2.10 and is unable to use -Dlog4j2.formatMsgNoLookups=true.
This is needed because of a major vulnerability introduced by the class' functionality, see more here: https://github.com/apache/logging-log4j2/pull/608
NOTE: This fixes BOTH CVE-2021-44228 / CVE-2021-45046 (A.K.A Log4Shell and an unnamed, but very similar exploit)
Java Application: resides in this repository (see releases), that removes JndiLookup.class from any log4j builds you feed via a GUI. Hard removal of the class on the server-side forcibly closing the vulnerability.
Forge Mod (CurseForge Link): A Minecraft mod developed for MinecraftForge for Minecraft versions 1.12.2 and lower, a softer, but hacky fix than the aforementioned method.