AccessControlException when trying to launch a JNLP file

[Mauro]

When trying to launch a JNLP file with 1.8 version of IcedTeaWeb bundled with Kubuntu 20.04, I get the following exception:

xception in thread "<app name>" java.lang.RuntimeException: java.lang.ExceptionInInitializerError
        at net.sourceforge.jnlp.Launcher$TgThread.run(Launcher.java:968)
Caused by: java.lang.ExceptionInInitializerError
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:566)
        at net.sourceforge.jnlp.Launcher.launchApplication(Launcher.java:576)
        at net.sourceforge.jnlp.Launcher$TgThread.run(Launcher.java:945)
Caused by: java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "getClassLoader")
        at java.base/java.security.AccessControlContext.checkPermission(AccessControlContext.java:472)
        at java.base/java.security.AccessController.checkPermission(AccessController.java:897)
        at java.base/java.lang.SecurityManager.checkPermission(SecurityManager.java:322)
        at net.sourceforge.jnlp.runtime.JNLPSecurityManager.checkPermission(JNLPSecurityManager.java:292)
        at java.base/java.lang.ClassLoader.checkClassLoaderPermission(ClassLoader.java:2060)
        at java.base/java.lang.Thread.getContextClassLoader(Thread.java:1492)
        at java.scripting/javax.script.ScriptEngineManager.<init>(ScriptEngineManager.java:61)
        at org.apache.logging.log4j.core.script.ScriptManager.<init>(ScriptManager.java:68)
        at org.apache.logging.log4j.core.config.AbstractConfiguration.initialize(AbstractConfiguration.java:214)
        at org.apache.logging.log4j.core.config.AbstractConfiguration.start(AbstractConfiguration.java:244)
        at org.apache.logging.log4j.core.LoggerContext.setConfiguration(LoggerContext.java:545)
        at org.apache.logging.log4j.core.LoggerContext.reconfigure(LoggerContext.java:617)
        at org.apache.logging.log4j.core.LoggerContext.reconfigure(LoggerContext.java:634)
        at org.apache.logging.log4j.core.LoggerContext.start(LoggerContext.java:229)
        at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:152)
        at org.apache.logging.log4j.core.impl.Log4jContextFactory.getContext(Log4jContextFactory.java:45)
        at org.apache.logging.log4j.LogManager.getContext(LogManager.java:194)
        at org.apache.logging.log4j.spi.AbstractLoggerAdapter.getContext(AbstractLoggerAdapter.java:122)
        at org.apache.logging.slf4j.Log4jLoggerFactory.getContext(Log4jLoggerFactory.java:43)
        at org.apache.logging.log4j.spi.AbstractLoggerAdapter.getLogger(AbstractLoggerAdapter.java:46)
        at org.apache.logging.slf4j.Log4jLoggerFactory.getLogger(Log4jLoggerFactory.java:29)
        at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:358)
        at org.slf4j.LoggerFactory.getLogger(LoggerFactory.java:383)
        at my.package.MyApp.<clinit>(MyApp.java:44)
        ... 6 more

Please note that the application that I want to start is signed and that I gave all the necessary permissions to it. The error appears after I give consent to the app publisher/signer (and hit "Remember"), after I give consent to the source URL from which the JARs are downloaded (and hit "Remember" for the whole website) and after I give consent to install application shortcuts (as requested in the JNLP file). On subsequent attempts, no other question is asked to me and the exception occurs immediately.

Based on this upstream bug report:
https://github.com/AdoptOpenJDK/IcedTea-Web/issues/324

it seems like the problem is fixed at least in IcedTeaWeb version 1.8.2.
I personally tested the latest version 1.8.4 and it fixed the problem for me.

In light of this, can the IcedTeaWeb package bundled in Ubuntu 20.04, which is at version 1.8, be updated to a newer 1.8.x version that fixes this problem?

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: icedtea-netx 1.8-0ubuntu8
ProcVersionSignature: Ubuntu 5.4.0-66.74-generic 5.4.86
Uname: Linux 5.4.0-66-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.16
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: KDE
Date: Wed Mar 3 10:21:09 2021
InstallationDate: Installed on 2020-10-05 (148 days ago)
InstallationMedia: Kubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: icedtea-web
UpgradeStatus: No upgrade log present (probably fresh install)