Seems to be a false positive:

http://seclists.org/bugtraq/2013/Jan/50
Cannot reproduce it on my site too. Also the google dork in the advisory is for nextgen-gallery

data/plugin_vulns.xml

@@ -923,11 +923,6 @@ File Upload Vulnerability</title>
       <reference>http://www.exploit-db.com/exploits/18998/</reference>
       <type>UPLOAD</type>
     </vulnerability>
-    <vulnerability>
-      <title>Gallery 3.8.3 Arbitrary File Read</title>
-      <reference>http://packetstormsecurity.com/files/119458/wpgallery-fileread.txt</reference>
-      <type>LFI</type>
-    </vulnerability>
   </plugin>
 
   <plugin name="font-uploader">