diff --git a/pom.xml b/pom.xml
index fcfa5f9e..6c2b3a6a 100644
--- a/pom.xml
+++ b/pom.xml
@@ -156,7 +156,7 @@
             <dependency>
                 <groupId>com.thoughtworks.xstream</groupId>
                 <artifactId>xstream</artifactId>
-                <version>1.4.20</version>
+                <version>1.4.21</version>
             </dependency>
             <!-- Transitive of both commons-httpclient (as v1.2) and courses-portlet-dao
                  (as v1.6). You'd think Maven would favor the higher version number, but