diff --git a/ANNOUNCE b/ANNOUNCE
index 2dfb5e3bf..16e7e6685 100644
--- a/ANNOUNCE
+++ b/ANNOUNCE
@@ -1,5 +1,5 @@
 
-Libpng 1.5.23beta01 - May 10, 2015
+Libpng 1.5.23beta01 - May 21, 2015
 
 This is not intended to be a public release.  It will be replaced
 within a few weeks by a public version or by another test version.
@@ -27,7 +27,7 @@ Other information:
 
 Changes since the last public release (1.5.22):
 
-Version 1.5.23beta01 [May 10, 2015]
+Version 1.5.23beta01 [May 21, 2015]
   Removed unused PNG_SET_CHUNK_[CACHE|MALLOC]_LIMIT_SUPPORTED definitions
     from pnglibconf.h.prebuilt (Andrew Church).
   Replaced "unexpected" with an integer in pngset.c where a long was
@@ -35,6 +35,8 @@ Version 1.5.23beta01 [May 10, 2015]
   Fix typecast in a png_debug2() statement in png_set_text_2() to
     avoid a compiler warning in PNG_DEBUG builds.
   Avoid Coverity issue 80858 (REVERSE NULL) in pngtest.c PNG_DEBUG builds.
+  Avoid a harmless potential integer overflow in png_XYZ_from_xy() (Bug
+    report from Christopher Ferris).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/CHANGES b/CHANGES
index 2752af3bd..9d1ce1e1a 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,11 +1,14 @@
 #if 0
 CHANGES - changes for libpng
 
-Version 0.2
+version 0.1 [March 29, 1995]
+  initial work-in-progress release
+
+version 0.2 [April 1, 1995]
   added reader into png.h
   fixed small problems in stub file
 
-Version 0.3
+version 0.3 [April 8, 1995]
   added pull reader
   split up pngwrite.c to several files
   added pnglib.txt
@@ -14,9 +17,9 @@ Version 0.3
   fixed some bugs in writer
   interfaced with zlib 0.5
   added K&R support
-  added check for 64 KB blocks for 16-bit machines
+  added check for 64 KB blocks for 16 bit machines
 
-Version 0.4
+version 0.4 [April 26, 1995]
   cleaned up code and commented code
   simplified time handling into png_time
   created png_color_16 and png_color_8 to handle color needs
@@ -27,28 +30,29 @@ Version 0.4
   cleaned up zTXt reader and writer (using zlib's Reset functions)
   split transformations into pngrtran.c and pngwtran.c
 
-Version 0.5
+version 0.5 [April 30, 1995]
   interfaced with zlib 0.8
   fixed many reading and writing bugs
   saved using 3 spaces instead of tabs
 
-Version 0.6
+version 0.6 [May 1, 1995]
+  first beta release
   added png_large_malloc() and png_large_free()
   added png_size_t
   cleaned up some compiler warnings
   added png_start_read_image()
 
-Version 0.7
+version 0.7 [June 24, 1995]
   cleaned up lots of bugs
   finished dithering and other stuff
   added test program
   changed name from pnglib to libpng
 
-Version 0.71 [June, 1995]
+version 0.71 [June 26, 1995]
   changed pngtest.png for zlib 0.93
   fixed error in libpng.txt and example.c
 
-Version 0.8
+version 0.8 [August 20, 1995]
   cleaned up some bugs
   added png_set_filler()
   split up pngstub.c into pngmem.c, pngio.c, and pngerror.c
@@ -1449,8 +1453,9 @@ Version 1.2.6beta4 [July 28, 2004]
   Use png_malloc instead of png_zalloc to allocate the pallete.
 
 Version 1.0.16rc1 and 1.2.6rc1 [August 4, 2004]
-  Fixed buffer overflow vulnerability in png_handle_tRNS()
-  Fixed integer arithmetic overflow vulnerability in png_read_png().
+  Fixed buffer overflow vulnerability (CVE-2004-0597) in png_handle_tRNS().
+  Fixed NULL dereference vulnerability (CVE-2004-0598) in png_handle_iCCP().
+  Fixed integer overflow vulnerability (CVE-2004-0599) in png_read_png().
   Fixed some harmless bugs in png_handle_sBIT, etc, that would cause
     duplicate chunk types to go undetected.
   Fixed some timestamps in the -config version
@@ -4334,7 +4339,7 @@ Version 1.5.22rc04 [March 16, 2015]
 Version 1.5.22 [March 26, 2015]
   No changes.
 
-Version 1.5.23beta01 [May 10, 2015]
+Version 1.5.23beta01 [May 21, 2015]
   Removed unused PNG_SET_CHUNK_[CACHE|MALLOC]_LIMIT_SUPPORTED definitions
     from pnglibconf.h.prebuilt (Andrew Church).
   Replaced "unexpected" with an integer in pngset.c where a long was
@@ -4342,6 +4347,8 @@ Version 1.5.23beta01 [May 10, 2015]
   Fix typecast in a png_debug2() statement in png_set_text_2() to
     avoid a compiler warning in PNG_DEBUG builds.
   Avoid Coverity issue 80858 (REVERSE NULL) in pngtest.c PNG_DEBUG builds.
+  Avoid a harmless potential integer overflow in png_XYZ_from_xy() (Bug
+    report from Christopher Ferris).
 
 Send comments/corrections/commendations to png-mng-implement at lists.sf.net
 (subscription required; visit
diff --git a/png.c b/png.c
index 2d7506463..c5794a91d 100644
--- a/png.c
+++ b/png.c
@@ -648,13 +648,13 @@ png_get_copyright(png_const_structp png_ptr)
 #else
 #  ifdef __STDC__
    return PNG_STRING_NEWLINE \
-     "libpng version 1.5.23beta01 - March 26, 2015" PNG_STRING_NEWLINE \
+     "libpng version 1.5.23beta01 - May 21, 2015" PNG_STRING_NEWLINE \
      "Copyright (c) 1998-2015 Glenn Randers-Pehrson" PNG_STRING_NEWLINE \
      "Copyright (c) 1996-1997 Andreas Dilger" PNG_STRING_NEWLINE \
      "Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc." \
      PNG_STRING_NEWLINE;
 #  else
-      return "libpng version 1.5.23beta01 - March 26, 2015\
+      return "libpng version 1.5.23beta01 - May 21, 2015\
       Copyright (c) 1998-2015 Glenn Randers-Pehrson\
       Copyright (c) 1996-1997 Andreas Dilger\
       Copyright (c) 1995-1996 Guy Eric Schalnat, Group 42, Inc.";
@@ -885,7 +885,8 @@ int png_XYZ_from_xy(png_XYZ *XYZ, png_xy xy)
 
    /* Check xy and, implicitly, z.  Note that wide gamut color spaces typically
     * have end points with 0 tristimulus values (these are impossible end
-    * points, but they are used to cover the possible colors.)
+    * points, but they are used to cover the possible colors).  We check
+    * xy.whitey against 5, not 0, to avoid a possible integer overflow.
     */
    if (xy.redx < 0 || xy.redx > PNG_FP_1) return 1;
    if (xy.redy < 0 || xy.redy > PNG_FP_1-xy.redx) return 1;
@@ -894,7 +895,7 @@ int png_XYZ_from_xy(png_XYZ *XYZ, png_xy xy)
    if (xy.bluex < 0 || xy.bluex > PNG_FP_1) return 1;
    if (xy.bluey < 0 || xy.bluey > PNG_FP_1-xy.bluex) return 1;
    if (xy.whitex < 0 || xy.whitex > PNG_FP_1) return 1;
-   if (xy.whitey < 0 || xy.whitey > PNG_FP_1-xy.whitex) return 1;
+   if (xy.whitey < 5 || xy.whitey > PNG_FP_1-xy.whitex) return 1;
 
    /* The reverse calculation is more difficult because the original tristimulus
     * value had 9 independent values (red,green,blue)x(X,Y,Z) however only 8