Joomla and all of its extensions are written in PHP.
log4j is Java software. It is not PHP software.
(Please note that Java and Javascript are completely different languages. They share absolutely nothing, not even syntax. Why is it called Javascript? It had to do with Netscape's misguided marketing in the 1990s.)
Therefore there is no action necessary for this issue as far as Joomla and its extensions are concerned since nothing in Joomla and its extensions is written in Java, therefore it cannot possible use log4j.
Nicholas K. Dionysopoulos
Lead Developer and Director
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