diff --git a/changelog.html b/changelog.html
index fc119ef381..79c403addd 100644
--- a/changelog.html
+++ b/changelog.html
@@ -55,7 +55,9 @@ Upcoming changes</a>
 <!-- Record your changes in the trunk here. -->
 <div id="trunk" style="display:none"><!--=TRUNK-BEGIN=-->
 <ul class=image>
-  <li class=>
+  <li class=bug>
+    HTML metacharacters not escaped in log messages.
+    (<a href="https://issues.jenkins-ci.org/browse/JENKINS-20800">issue 20800</a>)
 </ul>
 </div><!--=TRUNK-END=-->
 
diff --git a/core/src/main/java/hudson/Functions.java b/core/src/main/java/hudson/Functions.java
index 5c9554704f..50c115a850 100644
--- a/core/src/main/java/hudson/Functions.java
+++ b/core/src/main/java/hudson/Functions.java
@@ -135,7 +135,6 @@ import jenkins.model.ModelObjectWithContextMenu;
 
 import org.acegisecurity.providers.anonymous.AnonymousAuthenticationToken;
 import org.apache.commons.jelly.JellyContext;
-import org.apache.commons.jelly.JellyException;
 import org.apache.commons.jelly.JellyTagException;
 import org.apache.commons.jelly.Script;
 import org.apache.commons.jelly.XMLOutput;
@@ -144,19 +143,15 @@ import org.apache.commons.jexl.util.Introspector;
 import org.apache.commons.lang.StringUtils;
 import org.jvnet.tiger_types.Types;
 import org.kohsuke.stapler.Ancestor;
-import org.kohsuke.stapler.MetaClass;
 import org.kohsuke.stapler.Stapler;
 import org.kohsuke.stapler.StaplerRequest;
 import org.kohsuke.stapler.StaplerResponse;
-import org.kohsuke.stapler.WebApp;
 import org.kohsuke.stapler.jelly.InternationalizedStringExpression.RawHtmlArgument;
-import org.kohsuke.stapler.jelly.JellyClassTearOff;
 
 import com.google.common.base.Predicate;
 import com.google.common.base.Predicates;
 import java.util.concurrent.atomic.AtomicLong;
 import org.kohsuke.accmod.Restricted;
-import org.kohsuke.accmod.restrictions.DoNotUse;
 import org.kohsuke.accmod.restrictions.NoExternalUse;
 
 /**
@@ -450,13 +445,14 @@ public class Functions {
         return formatter.format(r);
     }
 
-    @Restricted(DoNotUse.class)
+    @Restricted(NoExternalUse.class)
     public static String[] printLogRecordHtml(LogRecord r, LogRecord prior) {
         String[] oldParts = prior == null ? new String[4] : logRecordPreformat(prior);
         String[] newParts = logRecordPreformat(r);
         for (int i = 0; i < /* not 4 */3; i++) {
             newParts[i] = "<span class='" + (newParts[i].equals(oldParts[i]) ? "logrecord-metadata-old" : "logrecord-metadata-new") + "'>" + newParts[i] + "</span>";
         }
+        newParts[3] = Util.xmlEscape(newParts[3]);
         return newParts;
     }
     /**
diff --git a/core/src/test/java/hudson/FunctionsTest.java b/core/src/test/java/hudson/FunctionsTest.java
index cafa59670c..8d13742cac 100644
--- a/core/src/test/java/hudson/FunctionsTest.java
+++ b/core/src/test/java/hudson/FunctionsTest.java
@@ -37,6 +37,8 @@ import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
 import java.util.Locale;
+import java.util.logging.Level;
+import java.util.logging.LogRecord;
 
 import jenkins.model.Jenkins;
 
@@ -293,4 +295,12 @@ public class FunctionsTest {
         assertEquals("H<wbr>,e<wbr>.l<wbr>/l<wbr>:o<wbr>-w<wbr>_o<wbr>=+|d", Functions.breakableString("H,e.l/l:o-w_o=+|d"));
         assertEquals("ALongStrin<wbr>gThatCanNo<wbr>tBeBrokenB<wbr>yDefault", Functions.breakableString("ALongStringThatCanNotBeBrokenByDefault"));
     }
+
+    @Bug(20800)
+    @Test public void printLogRecordHtml() throws Exception {
+        LogRecord lr = new LogRecord(Level.INFO, "Bad input <xml/>");
+        lr.setLoggerName("test");
+        assertEquals("Bad input &lt;xml/>\n", Functions.printLogRecordHtml(lr, null)[3]);
+    }
+
 }