Files::copy requires an undocumented permission when copying from the default file system to a non-default file system. This is a change in behaviour from JDK 18 to JDK 19-ea, introduced by JDK-8267820.

Example reproducer:

$ cat FileCopyToZip.java
import java.io.*;
import java.nio.file.*;
import java.util.*;

public class FileCopyToZip {

    public static void main(String... args) throws IOException {
        Path source = Path.of(args[0]);
        Path zip = Path.of("out.zip");
        Map<String,String> env = Map.of("create", String.valueOf(Files.notExists(zip)));
        
        try (FileSystem fileSystem = FileSystems.newFileSystem(zip, env, FileCopyToZip.class.getClassLoader())) {
            Path p = fileSystem.getPath(source.getFileName().toString());
            Files.copy(source, p);
        }
    }
}

$ /Users/chegar/binaries/jdk-18.jdk/Contents/Home/bin/javac FileCopyToZip.java

$ cat java.policy
grant {
    permission java.io.FilePermission "<<ALL FILES>>", "read,write";
};

$ /Users/chegar/binaries/jdk-18.jdk/Contents/Home/bin/java -Djava.security.manager -Djava.security.policy=java.policy FileCopyToZip FileCopyToZip.class
WARNING: A command line option has enabled the Security Manager
WARNING: The Security Manager is deprecated and will be removed in a future release


$ /Users/chegar/binaries/jdk-19.jdk/Contents/Home/bin/java -Djava.security.manager -Djava.security.policy=java.policy FileCopyToZip FileCopyToZip.class
WARNING: A command line option has enabled the Security Manager
WARNING: The Security Manager is deprecated and will be removed in a future release
Exception in thread "main" java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "accessUserInformation")
at java.base/java.security.AccessControlContext.checkPermission(AccessControlContext.java:485)
at java.base/java.security.AccessController.checkPermission(AccessController.java:1068)
at java.base/java.lang.SecurityManager.checkPermission(SecurityManager.java:411)
at java.base/sun.nio.fs.UnixFileAttributeViews$Posix.checkReadExtended(UnixFileAttributeViews.java:186)
at java.base/sun.nio.fs.UnixFileAttributeViews$Posix.readAttributes(UnixFileAttributeViews.java:253)
at java.base/sun.nio.fs.UnixFileAttributeViews$Posix.readAttributes(UnixFileAttributeViews.java:168)
at java.base/sun.nio.fs.UnixFileSystemProvider.readAttributes(UnixFileSystemProvider.java:148)
at java.base/java.nio.file.Files.readAttributes(Files.java:1851)
at java.base/java.nio.file.CopyMoveHelper.copyToForeignTarget(CopyMoveHelper.java:114)
at java.base/java.nio.file.Files.copy(Files.java:1308)
at FileCopyToZip.main(FileCopyToZip.java:14)