A critical vulnerability was recently discovered related to systems/software that run Apache Log4j
More information about this vulnerability can be found here. National Vulnerability Ddatabase - CVE-2021-44228 (nist.gov)
This is an industry-wide vulnerability affecting the Apache Log4j itself and is not specific to Unified Communications Diagnostic.
Unified Communication Diagnostics does not use Apache Log4j, therefore is not affected by CVE-2021-44228.