Applications that use or depend on the Apache Commons Text library are affected—but not all applications. In addition to having a vulnerable version of Apache Commons Text, the application code must have a certain vulnerable pattern.
Text4Shell can only be exploited if the target system is running certain default interpolators in versions 1.5-1.9 (inclusive) of Apache Commons Text. String interpolation is the practice of mixing strings and integers to build new strings, and is a common threat vector in applications.