diff --git a/src/main/java/ch/ethz/seb/sebserver/gui/content/exam/LmsSetupForm.java b/src/main/java/ch/ethz/seb/sebserver/gui/content/exam/LmsSetupForm.java
index fcac8ab8..a980c810 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gui/content/exam/LmsSetupForm.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gui/content/exam/LmsSetupForm.java
@@ -15,6 +15,7 @@ import java.util.function.BooleanSupplier;
 import java.util.function.Function;
 
 import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.text.StringEscapeUtils;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.widgets.Button;
 import org.eclipse.swt.widgets.Composite;
@@ -481,7 +482,7 @@ public class LmsSetupForm implements TemplateComposer {
                 case TOKEN_REQUEST: {
                     throw new PageMessageException(new LocTextKey(
                             "sebserver.lmssetup.action.test.tokenRequestError",
-                            Utils.formatHTMLLinesForceEscaped(Utils.escapeHTML_XML_EcmaScript(error.message))));
+                            Utils.formatHTMLLinesForceEscaped(StringEscapeUtils.escapeHtml4(error.message))));
                 }
                 case QUIZ_ACCESS_API_REQUEST: {
                     if (error.message.contains("quizaccess_sebserver_get_exams")) {
diff --git a/src/main/java/ch/ethz/seb/sebserver/gui/service/i18n/impl/PolyglotPageServiceImpl.java b/src/main/java/ch/ethz/seb/sebserver/gui/service/i18n/impl/PolyglotPageServiceImpl.java
index 1ddf4989..1a669a7f 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gui/service/i18n/impl/PolyglotPageServiceImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gui/service/i18n/impl/PolyglotPageServiceImpl.java
@@ -11,7 +11,9 @@ package ch.ethz.seb.sebserver.gui.service.i18n.impl;
 import java.util.Locale;
 import java.util.function.Consumer;
 
+import org.apache.commons.lang3.BooleanUtils;
 import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.text.StringEscapeUtils;
 import org.eclipse.rap.rwt.RWT;
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.widgets.Button;
@@ -30,6 +32,8 @@ import org.eclipse.swt.widgets.TableItem;
 import org.eclipse.swt.widgets.Text;
 import org.eclipse.swt.widgets.Tree;
 import org.eclipse.swt.widgets.TreeItem;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 import org.springframework.context.annotation.Lazy;
 import org.springframework.stereotype.Service;
 
@@ -49,6 +53,8 @@ import ch.ethz.seb.sebserver.gui.widget.Selection;
 @GuiProfile
 public final class PolyglotPageServiceImpl implements PolyglotPageService {
 
+    private static final Logger log = LoggerFactory.getLogger(PolyglotPageServiceImpl.class);
+
     private final I18nSupport i18nSupport;
 
     public PolyglotPageServiceImpl(final I18nSupport i18nSupport) {
@@ -93,7 +99,11 @@ public final class PolyglotPageServiceImpl implements PolyglotPageService {
 
     @Override
     public void injectI18n(final Label label, final LocTextKey locTextKey) {
-        injectI18n(label, locTextKey, null);
+        try {
+            injectI18n(label, locTextKey, null);
+        } catch (final Exception e) {
+            log.error("Failed to injectI18n: {}", e.getMessage());
+        }
     }
 
     @Override
@@ -269,8 +279,14 @@ public final class PolyglotPageServiceImpl implements PolyglotPageService {
             final I18nSupport i18nSupport) {
 
         return label -> {
+
             if (locTextKey != null) {
-                label.setText(i18nSupport.getText(locTextKey));
+                final String text = i18nSupport.getText(locTextKey);
+                if (BooleanUtils.toBoolean((Boolean) label.getData(RWT.MARKUP_ENABLED))) {
+                    label.setText(StringEscapeUtils.escapeHtml4(text));
+                } else {
+                    label.setText(text);
+                }
             }
             if (i18nSupport.hasText(locToolTipKey)) {
                 label.setToolTipText(Utils.formatLineBreaks(i18nSupport.getText(locToolTipKey)));
diff --git a/src/main/java/ch/ethz/seb/sebserver/gui/widget/Message.java b/src/main/java/ch/ethz/seb/sebserver/gui/widget/Message.java
index df09b0f0..9913deec 100644
--- a/src/main/java/ch/ethz/seb/sebserver/gui/widget/Message.java
+++ b/src/main/java/ch/ethz/seb/sebserver/gui/widget/Message.java
@@ -10,6 +10,7 @@ package ch.ethz.seb.sebserver.gui.widget;
 
 import java.util.Locale;
 
+import org.apache.commons.text.StringEscapeUtils;
 import org.eclipse.rap.rwt.RWT;
 import org.eclipse.rap.rwt.widgets.DialogCallback;
 import org.eclipse.swt.graphics.Rectangle;
@@ -17,7 +18,6 @@ import org.eclipse.swt.layout.GridLayout;
 import org.eclipse.swt.widgets.MessageBox;
 import org.eclipse.swt.widgets.Shell;
 
-import ch.ethz.seb.sebserver.gbl.util.Utils;
 import ch.ethz.seb.sebserver.gui.service.i18n.I18nSupport;
 import ch.ethz.seb.sebserver.gui.widget.WidgetFactory.CustomVariant;
 
@@ -46,7 +46,7 @@ public final class Message extends MessageBox {
             super.prepareOpen();
         } catch (final IllegalArgumentException e) {
             // fallback on markup text error
-            super.setMessage(Utils.escapeHTML_XML_EcmaScript(super.getMessage()));
+            super.setMessage(StringEscapeUtils.escapeHtml4(super.getMessage()));
             super.prepareOpen();
         }
         final GridLayout layout = (GridLayout) super.shell.getLayout();
diff --git a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/proctoring/ExamProctoringRoomServiceImpl.java b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/proctoring/ExamProctoringRoomServiceImpl.java
index 891c4a9e..e0c469a8 100644
--- a/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/proctoring/ExamProctoringRoomServiceImpl.java
+++ b/src/main/java/ch/ethz/seb/sebserver/webservice/servicelayer/session/impl/proctoring/ExamProctoringRoomServiceImpl.java
@@ -326,6 +326,11 @@ public class ExamProctoringRoomServiceImpl implements ExamProctoringRoomService
                             cc.getExamId(),
                             cc.getConnectionToken());
 
+                    if (proctoringRoom == null) {
+                        log.warn("Assign SEB client to proctoring room failed for: {}", cc);
+                        return;
+                    }
+
                     if (log.isDebugEnabled()) {
                         log.debug("Assigning new SEB client to proctoring room: {}, connection: {}",
                                 proctoringRoom.id,