diff --git a/jspwiki-main/src/main/java/org/apache/wiki/WikiSession.java b/jspwiki-main/src/main/java/org/apache/wiki/WikiSession.java
index d2b6fae9aa..dab9059a4f 100644
--- a/jspwiki-main/src/main/java/org/apache/wiki/WikiSession.java
+++ b/jspwiki-main/src/main/java/org/apache/wiki/WikiSession.java
@@ -150,6 +150,14 @@ public String antiCsrfToken() {
         return antiCsrfToken;
     }
 
+    /**
+     * Regenerates the anti-CSRF token. Called when the session's privilege level changes (i.e. at login), so that
+     * a token observed before authentication cannot be replayed against the authenticated session.
+     */
+    public void regenerateAntiCsrfToken() {
+        antiCsrfToken = UUID.randomUUID().toString();
+    }
+
     /** {@inheritDoc} */
     @Override
     public Locale getLocale() {
diff --git a/jspwiki-main/src/main/java/org/apache/wiki/auth/DefaultAuthenticationManager.java b/jspwiki-main/src/main/java/org/apache/wiki/auth/DefaultAuthenticationManager.java
index 6734e094d6..287ec3747f 100644
--- a/jspwiki-main/src/main/java/org/apache/wiki/auth/DefaultAuthenticationManager.java
+++ b/jspwiki-main/src/main/java/org/apache/wiki/auth/DefaultAuthenticationManager.java
@@ -55,6 +55,7 @@ Licensed to the Apache Software Foundation (ASF) under one
 import java.util.Properties;
 import java.util.Set;
 import org.apache.wiki.WikiContext;
+import org.apache.wiki.WikiSession;
 import org.apache.wiki.auth.user.UserProfile;
 
 
@@ -178,6 +179,7 @@ public boolean login( final HttpServletRequest request ) throws WikiSecurityExce
 
             // If the container logged the user in successfully, tell the Session (and add all the Principals)
             if (!principals.isEmpty()) {
+                rotateSessionAfterAuthentication( request, session );
                 fireEvent( WikiSecurityEvent.LOGIN_AUTHENTICATED, getLoginPrincipal( principals ), session, request );
                 for( final Principal principal : principals ) {
                     fireEvent( WikiSecurityEvent.PRINCIPAL_ADD, principal, session, request );
@@ -269,6 +271,7 @@ public boolean login( final Session session, final HttpServletRequest request, f
         // Execute the user's specified login module
         final Set< Principal > principals = doJAASLogin( m_loginModuleClass, handler, m_loginModuleOptions );
         if(!principals.isEmpty()) {
+            rotateSessionAfterAuthentication( request, session );
             fireEvent(WikiSecurityEvent.LOGIN_AUTHENTICATED, getLoginPrincipal( principals ), session, request );
             for ( final Principal principal : principals ) {
                 fireEvent( WikiSecurityEvent.PRINCIPAL_ADD, principal, session, request );
@@ -282,6 +285,34 @@ public boolean login( final Session session, final HttpServletRequest request, f
         return false;
     }
 
+    /**
+     * Session-fixation defense: the pre-authentication HTTP session id and anti-CSRF token must not survive the
+     * upgrade to an authenticated session. Rotates the servlet session id, re-keys the {@link SessionMonitor} entry
+     * so the wiki session attaches to the new id, and regenerates the wiki session's anti-CSRF token so a token
+     * observed before login cannot be replayed against the authenticated session.
+     *
+     * @param request the servlet request, may be <code>null</code> (e.g. embedded use); nothing to rotate then
+     * @param session the wiki session being upgraded
+     */
+    private void rotateSessionAfterAuthentication( final HttpServletRequest request, final Session session ) {
+        if( request != null ) {
+            final HttpSession httpSession = request.getSession( false );
+            if( httpSession != null ) {
+                final SessionMonitor monitor = SessionMonitor.getInstance( m_engine );
+                monitor.remove( httpSession );
+                try {
+                    request.changeSessionId();
+                } catch( final IllegalStateException e ) {
+                    LOG.debug( "Unable to rotate the http session id: {}", e.getMessage() );
+                }
+                monitor.register( httpSession, session );
+            }
+        }
+        if( session instanceof WikiSession ) {
+            ( ( WikiSession )session ).regenerateAntiCsrfToken();
+        }
+    }
+
     /**
      *  This method builds a database of login names that are being attempted, and will try to delay if there are too many requests coming
      *  in for the same username.
diff --git a/jspwiki-main/src/main/java/org/apache/wiki/auth/SessionMonitor.java b/jspwiki-main/src/main/java/org/apache/wiki/auth/SessionMonitor.java
index 76c1ab6f0d..37f03f2b19 100644
--- a/jspwiki-main/src/main/java/org/apache/wiki/auth/SessionMonitor.java
+++ b/jspwiki-main/src/main/java/org/apache/wiki/auth/SessionMonitor.java
@@ -206,6 +206,23 @@ public final void remove( final HttpSession session ) {
         }
     }
 
+    /**
+     * (Re-)associates a wiki session with the user's current HTTP session id. Needed after the HTTP session id has
+     * been rotated at authentication time (session-fixation defense), so that the upgraded privileges attach to the
+     * new session id instead of the pre-login one.
+     *
+     * @param session the user's HTTP session, carrying its current id
+     * @param wikiSession the wiki session to register under that id
+     */
+    public final void register( final HttpSession session, final Session wikiSession ) {
+        if( session == null || wikiSession == null ) {
+            throw new IllegalArgumentException( "Session cannot be null." );
+        }
+        synchronized( m_sessions ) {
+            m_sessions.put( session.getId(), wikiSession );
+        }
+    }
+
     /**
      * Returns the current number of active wiki sessions.
      * @return the number of sessions