diff -ur cfitsio-3.47/drvrnet.c cfitsio-3.47.sformat/drvrnet.c
--- cfitsio-3.47/drvrnet.c	2019-05-21 21:41:54.000000000 +0200
+++ cfitsio-3.47.sformat/drvrnet.c	2019-08-01 13:52:41.461958938 +0200
@@ -1257,9 +1257,9 @@
          urlname = (char *)clientp;
          if (urlname)
          {
-            fprintf(stderr,"Downloading ");
-            fprintf(stderr,urlname);
-            fprintf(stderr,"...\n");
+            fprintf(stderr,"%s","Downloading ");
+            fprintf(stderr,"%s",urlname);
+            fprintf(stderr,"%s","...\n");
          }
          isFirst = 0;
       }
@@ -1270,13 +1270,13 @@
          nToDisplay = fullBar;
       fprintf(stderr,"%3d%% [",percent);
       for (i=0; i<nToDisplay; ++i)
-         fprintf(stderr,"=");
+         fprintf(stderr,"%s","=");
       /* print remaining spaces */
       for (i=nToDisplay; i<fullBar; ++i)
-         fprintf(stderr," ");
-      fprintf(stderr,"]\r");
+         fprintf(stderr,"%s"," ");
+      fprintf(stderr,"%s","]\r");
       if (isComplete)
-         fprintf(stderr,"\n");
+         fprintf(stderr,"%s","\n");
       fflush(stderr);
    }
    return 0;
Sólo en cfitsio-3.47: .drvrnet.c.swp