A sandbox bypass vulnerability exists in Script Security Plugin 1.47 and earlier in groovy-sandbox/src/main/java/org/kohsuke/groovy/sandbox/SandboxTransformer.java that allows attackers with Job/Configure permission to execute arbitrary code on the Jenkins master JVM, if plugins using the Groovy sandbox are installed.
In Jenkins Script Security Plugin version 1.36 and earlier, users with the ability to configure sandboxed Groovy scripts are able to use a type coercion feature in Groovy to create new `File` objects from strings. This allowed reading arbitrary files on the Jenkins master file system. Such a type coercion is now subject to sandbox protection and considered to be a call to the `new File(String)` constructor for the purpose of in-process script approval.
Script Security Plugin did not apply sandboxing restrictions to constructor invocations via positional arguments list, super constructor invocations, method references, and type coercion expressions. This could be used to invoke arbitrary constructors and methods, bypassing sandbox protection.