disallow new in if condition attribute in config files

Signed-off-by: ceki <ceki@qos.ch>

Author: ceki

logback-core-blackbox/src/test/blackboxInput/joran/conditional/ifNew.xml

@@ -0,0 +1,14 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+
+<x>
+    <stack name="BEGIN"/>
+    <if condition='new Integer(1).equals(1)'>
+        <then>
+            <stack name="a"/>
+        </then>
+        <else>
+            <stack name="b"/>
+        </else>
+    </if>
+    <stack name="END"/>
+</x>

logback-core-blackbox/src/test/java/ch/qos/logback/core/blackbox/joran/conditional/IfThenElseTest.java

@@ -52,7 +52,6 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
-import java.io.IOException;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.Stack;
@@ -130,6 +129,16 @@ public void whenContextPropertyIsSet_IfThenBranchIsEvaluated() throws JoranExcep
         verifyConfig(new String[] { "BEGIN", "a", "END" });
     }
 
+    @Test
+    public void ifWithNew() throws JoranException {
+        context.putProperty(ki1, val1);
+        simpleConfigurator.doConfigure(CONDITIONAL_DIR_PREFIX + "ifNew.xml");
+        checker.containsMatch(Status.ERROR, IfModelHandler.NEW_OPERATOR_DISALLOWED_MSG);
+        checker.containsMatch(Status.ERROR, IfModelHandler.NEW_OPERATOR_DISALLOWED_SEE);
+        verifyConfig(new String[] { "BEGIN", "END" });
+    }
+
+
     @Test
     public void whenLocalPropertyIsSet_IfThenBranchIsEvaluated() throws JoranException {
         simpleConfigurator.doConfigure(CONDITIONAL_DIR_PREFIX + "if_localProperty.xml");

logback-core/src/main/java/ch/qos/logback/core/model/processor/conditional/IfModelHandler.java

@@ -1,6 +1,6 @@
 /**
  * Logback: the reliable, generic, fast and flexible logging framework.
- * Copyright (C) 1999-2022, QOS.ch. All rights reserved.
+ * Copyright (C) 1999-2025, QOS.ch. All rights reserved.
  *
  * This program and the accompanying materials are dual-licensed under
  * either the terms of the Eclipse Public License v1.0 as published by
@@ -33,6 +33,9 @@ public class IfModelHandler extends ModelHandlerBase {
     public static final String MISSING_JANINO_MSG = "Could not find Janino library on the class path. Skipping conditional processing.";
     public static final String MISSING_JANINO_SEE = "See also " + CoreConstants.CODES_URL + "#ifJanino";
 
+    public static final String NEW_OPERATOR_DISALLOWED_MSG = "The 'condition' attribute may not contain the 'new' operator.";
+    public static final String NEW_OPERATOR_DISALLOWED_SEE = "See also " + CoreConstants.CODES_URL + "#conditionNew";
+
     enum Branch {IF_BRANCH, ELSE_BRANCH; }
 
     IfModel ifModel = null;
@@ -75,6 +78,13 @@ public void handle(ModelInterpretationContext mic, Model model) throws ModelHand
                return;
             }
 
+            // do not allow 'new' operator
+            if(hasNew(conditionStr)) {
+                addError(NEW_OPERATOR_DISALLOWED_MSG);
+                addError(NEW_OPERATOR_DISALLOWED_SEE);
+                return;
+            }
+
             try {
                 PropertyEvalScriptBuilder pesb = new PropertyEvalScriptBuilder(mic);
                 pesb.setContext(context);
@@ -96,8 +106,12 @@ public void handle(ModelInterpretationContext mic, Model model) throws ModelHand
             }
         }
     }
-    
-    
+
+    private boolean hasNew(String conditionStr) {
+        return conditionStr.contains("new ");
+    }
+
+
     @Override
     public void postHandle(ModelInterpretationContext mic, Model model) throws ModelHandlerException {