if (!pgwin32_get_dynamic_tokeninfo(AccessToken, TokenGroups,
                                       &InfoBuffer, errbuf, sizeof(errbuf)))
    {
-       write_stderr(errbuf);
+       write_stderr("%s", errbuf);
        exit(1);
    }
 
    if (!pgwin32_get_dynamic_tokeninfo(AccessToken, TokenUser, &InfoBuffer,
                                       errbuf, sizeof(errbuf)))
    {
-       fprintf(stderr, errbuf);
+       fprintf(stderr, "%s", errbuf);
        return -1;
    }
 
    if (!pgwin32_get_dynamic_tokeninfo(AccessToken, TokenGroups, &InfoBuffer,
                                       errbuf, sizeof(errbuf)))
    {
-       fprintf(stderr, errbuf);
+       fprintf(stderr, "%s", errbuf);
        return -1;
    }