output: #fixed code
                                  public Object execute(Object ctx, Map tokens) {
          if (nodes == null) {
              return new String(expression);
          }
          else if (nodes.length == 2) {
              /**
               * This is an optimization for property expressions.
               */
              switch (nodes[0].getToken()) {
                  case PROPERTY_EX:
                      //noinspection unchecked
                      //  return ExpressionParser.eval(getInternalSegment(nodes[0]), ctx, tokens);
  
                      if (!cacheAggressively) {
                          char[] seg = new char[expression.length - 3];
                          arraycopy(expression, 2, seg, 0, seg.length);
  
                          return MVEL.eval(seg, ctx, tokens);
                      }
                      else {
                          String s = new String(expression, 2, expression.length - 3);
                          if (!EX_PRECOMP_CACHE.containsKey(s)) {
                              synchronized (EX_PRECOMP_CACHE) {
                                  EX_PRECOMP_CACHE.put(s, MVEL.compileExpression(s));
                                  return MVEL.executeExpression(EX_PRECOMP_CACHE.get(s), ctx, tokens);
                              }
                          }
                          else {
                              return MVEL.executeExpression(EX_PRECOMP_CACHE.get(s), ctx, tokens);
                          }
  
                      }
                  case LITERAL:
                      return new String(expression);
  
              }
  
              return new String(expression);
          }
  
          Object register = null;
  
          StringAppender sbuf = new StringAppender(10);
          Node currNode = null;
  
          try {
              ExpressionParser oParser = new ExpressionParser(ctx, tokens);
  
              initStack();
              pushAndForward();
  
              while ((currNode = pop()) != null) {
                  node = currNode.getNode();
  
                  switch (currNode.getToken()) {
                      case LITERAL: {
                          sbuf.append(register = new String(expression, currNode.getStartPos(),
                                  currNode.getEndPos() - currNode.getStartPos()));
                          break;
                      }
                      case PROPERTY_EX: {
                          sbuf.append(
                                  valueOf(register = oParser.setExpressionArray(getInternalSegment(currNode)).parse())
                          );
                          break;
                      }
                      case IF:
                      case ELSEIF: {
                          try {
                              if (!((Boolean) oParser.setExpressionArray(getInternalSegment(currNode)).parse())) {
                                  exitContext();
                              }
                          }
                          catch (ClassCastException e) {
                              throw new CompileException("IF expression does not return a boolean: " + new String(getSegment(currNode)));
                          }
                          break;
                      }
                      case FOREACH: {
                          ForeachContext foreachContext = (ForeachContext) currNode.getRegister();
                          if (foreachContext.getItererators() == null) {
                              try {
                                  String[] lists = getForEachSegment(currNode).split(",");
                                  Iterator[] iters = new Iterator[lists.length];
                                  for (int i = 0; i < lists.length; i++) {
                                      Object listObject = new ExpressionParser(lists[i], ctx, tokens).parse();
                                      if (listObject instanceof Object[]) {
                                          listObject = Arrays.asList((Object[]) listObject);
                                      }
                                      iters[i] = ((Collection) listObject).iterator();
                                  }
                                  foreachContext.setIterators(iters);
                              }
                              catch (ClassCastException e) {
                                  throw new CompileException("expression for collections does not return a collections object: " + new String(getSegment(currNode)));
                              }
                              catch (NullPointerException e) {
                                  throw new CompileException("null returned for foreach in expression: " + (getForEachSegment(currNode)));
                              }
                          }
  
                          Iterator[] iters = foreachContext.getItererators();
                          String[] alias = currNode.getAlias().split(",");
                          // must trim vars
                          for (int i = 0; i < alias.length; i++) {
                              alias[i] = alias[i].trim();
                          }
  
                          if (iters[0].hasNext()) {
                              push();
  
                              //noinspection unchecked
                              for (int i = 0; i < iters.length; i++) {
                                  tokens.put(alias[i], iters[i].next());
                              }
                              if (foreachContext.getCount() != 0) {
                                  sbuf.append(foreachContext.getSeperator());
                              }
                              foreachContext.setCount(foreachContext.getCount() + 1);
                          }
                          else {
                              for (int i = 0; i < iters.length; i++) {
                                  tokens.remove(alias[i]);
                              }
                              foreachContext.setIterators(null);
                              foreachContext.setCount(0);
                              exitContext();
                          }
                          break;
                      }
                      case ELSE:
                      case END:
                          if (stack.isEmpty()) forwardAndPush();
                          continue;
                      case GOTO:
                          pushNode(currNode.getEndNode());
                          continue;
                      case TERMINUS: {
                          if (nodes.length == 2) {
                              return register;
                          }
                          else {
                              return sbuf.toString();
                          }
                      }
                      case INCLUDE_BY_REF: {
                          IncludeRef includeRef = (IncludeRef) nodes[node].getRegister();
                          String template = EX_TEMPLATE_REGISTRY.get(includeRef.getName());
  
                          IncludeRefParam[] params = includeRef.getParams();
                          Map vars = new HashMap(params.length * 2);
                          for (int i = 0; i < params.length; i++) {
                              vars.put(params[i].getIdentifier(), MVEL.eval(params[i].getValue(), ctx, tokens));
                          }
  
                          sbuf.append(Interpreter.parse(template, ctx, vars));
                      }
                  }
  
                  forwardAndPush();
              }
              throw new CompileException("expression did not end properly: expected TERMINUS node");
          }
          catch (CompileException e) {
              throw e;
          }
          catch (Exception e) {
              if (currNode != null) {
                  throw new CompileException("problem encountered at node [" + currNode.getNode() + "] "
                          + currNode.getToken() + "{" + currNode.getStartPos() + "," + currNode.getEndPos() + "}", e);
              }
              throw new CompileException("unhandled fatal exception (node:" + node + ")", e);
          }
      }
input: #vulnerable code 
                                  public Object execute(Object ctx, Map tokens) {
          if (nodes == null) {
              return new String(expression);
          }
          else if (nodes.length == 2) {
              switch (nodes[0].getToken()) {
                  case PROPERTY_EX:
                      //noinspection unchecked
                      //  return ExpressionParser.eval(getInternalSegment(nodes[0]), ctx, tokens);
  
                      if (!cacheAggressively) {
                          char[] seg = new char[expression.length - 3];
                          arraycopy(expression, 2, seg, 0, seg.length);
  
                          return MVEL.eval(seg, ctx, tokens);
                      }
                      else {
                          String s = new String(expression, 2, expression.length - 3);
                          if (!EX_PRECOMP_CACHE.containsKey(s)) {
                              synchronized (EX_PRECOMP_CACHE) {
                                  EX_PRECOMP_CACHE.put(s, MVEL.compileExpression(s));
                                  return MVEL.executeExpression(EX_PRECOMP_CACHE.get(s), ctx, tokens);
                              }
                          }
                          else {
                              return MVEL.executeExpression(EX_PRECOMP_CACHE.get(s), ctx, tokens);
                          }
  
                      }
                  case LITERAL:
                      return new String(expression);
                  case INCLUDE_BY_REF: {
                      IncludeRef includeRef = (IncludeRef) nodes[0].getRegister();
                      String template = EX_TEMPLATE_REGISTRY.get( includeRef.getName() );
                      
                      IncludeRefParam[] params = includeRef.getParams();
                      Map vars = new HashMap( params.length );
                      for ( int i = 0; i < params.length; i++ ) {
                          vars.put( params[i].getIdentifier(), parse(params[i].getValue(), ctx, tokens));
                      }
                      
                      return Interpreter.parse( template, ctx, vars );                    
                  }                    
              }
  
              return new String(expression);
          }
  
          Object register = null;
  
          StringAppender sbuf = new StringAppender(10);
          Node currNode = null;
  
          try {
              ExpressionParser oParser = new ExpressionParser(ctx, tokens);
  
              initStack();
              pushAndForward();
  
              while ((currNode = pop()) != null) {
                  node = currNode.getNode();
  
                  switch (currNode.getToken()) {
                      case LITERAL: {
                          sbuf.append(register = new String(expression, currNode.getStartPos(),
                                  currNode.getEndPos() - currNode.getStartPos()));
                          break;
                      }
                      case PROPERTY_EX: {
                          sbuf.append(
                                  valueOf(register = oParser.setExpressionArray(getInternalSegment(currNode)).parse())
                          );
                          break;
                      }
                      case IF:
                      case ELSEIF: {
                          try {
                              if (!((Boolean) oParser.setExpressionArray(getInternalSegment(currNode)).parse())) {
                                  exitContext();
                              }
                          }
                          catch (ClassCastException e) {
                              throw new CompileException("IF expression does not return a boolean: " + new String(getSegment(currNode)));
                          }
                          break;
                      }
                      case FOREACH: {
                          ForeachContext foreachContext = ( ForeachContext ) currNode.getRegister();
                          if ( foreachContext.getItererators() == null ) {
                              try {
                                  String[] lists = getForEachSegment(currNode).split( "," );
                                  Iterator[] iters = new Iterator[lists.length];
                                  for( int i = 0; i < lists.length; i++ ) {
                                      Object listObject = new ExpressionParser(lists[i], ctx, tokens).parse();
                                      if ( listObject instanceof Object[]) {
                                          listObject = Arrays.asList( (Object[]) listObject );
                                      }    
                                      iters[i] = ((Collection)listObject).iterator() ;
                                  }
                                  foreachContext.setIterators( iters );
                              } catch (ClassCastException e) {
                                  throw new CompileException("expression for collections does not return a collections object: " + new String(getSegment(currNode)));
                              }
                              catch (NullPointerException e) {
                                  throw new CompileException("null returned for foreach in expression: " + (getForEachSegment(currNode)));
                              }
                          }
  
                          Iterator[] iters = foreachContext.getItererators();
                          String[] alias = currNode.getAlias().split( "," );
                          // must trim vars
                          for ( int i = 0; i < alias.length; i++ ) {
                              alias[i] = alias[i].trim();
                          }                         
                          
                          if (iters[0].hasNext()) {
                              push();
  
                              //noinspection unchecked
                              for ( int i = 0; i < iters.length; i++ ) {
                                  tokens.put(alias[i], iters[i].next());
                              }
                              if ( foreachContext.getCount() != 0 ) {
                                  sbuf.append( foreachContext.getSeperator() );
                              }
                              foreachContext.setCount( foreachContext.getCount( ) + 1 );
                          }
                          else {
                              for ( int i = 0; i < iters.length; i++ ) {
                                  tokens.remove(alias[i]);
                              }      
                              foreachContext.setIterators( null );
                              foreachContext.setCount( 0 );
                              exitContext();
                          }
                          break;
                      }
                      case ELSE:
                      case END:
                          if (stack.isEmpty()) forwardAndPush();
                          continue;
                      case GOTO:
                          pushNode(currNode.getEndNode());
                          continue;
                      case TERMINUS: {
                          if (nodes.length == 2) {
                              return register;
                          }
                          else {
                              return sbuf.toString();
                          }
                      }
                  }
  
                  forwardAndPush();
              }
              throw new CompileException("expression did not end properly: expected TERMINUS node");
          }
          catch (CompileException e) {
              throw e;
          }
          catch (Exception e) {
              if (currNode != null) {
                  throw new CompileException("problem encountered at node [" + currNode.getNode() + "] "
                          + currNode.getToken() + "{" + currNode.getStartPos() + "," + currNode.getEndPos() + "}", e);
              }
              throw new CompileException("unhandled fatal exception (node:" + node + ")", e);
          }
      } 
                              #location 39 
                              #vulnerability type THREAD_SAFETY_VIOLATION