diff --git a/gio/gdesktopappinfo.c b/gio/gdesktopappinfo.c
index 11b031bd388db5c8e2ef323272819e9bfcdad84d..18aa0b52598b19ec2319551927827c02f1eca48b 100644
--- a/gio/gdesktopappinfo.c
+++ b/gio/gdesktopappinfo.c
@@ -3313,7 +3313,7 @@ g_desktop_app_info_launch_with_kylin_process_manager (GDesktopAppInfo    *info,
   g_variant_builder_close (&builder);
 
   gboolean has_icon_geometry = FALSE;
-  if (g_object_get_data (launch_context, "rectX")) {
+  if (g_object_get_data (launch_context, "rectWidth")) {
     has_icon_geometry = TRUE;
     gint rect_x = GPOINTER_TO_INT(g_object_get_data(launch_context, "rectX"));
     gint rect_y = GPOINTER_TO_INT(g_object_get_data(launch_context, "rectY"));
diff --git a/glib/gdatetime.c b/glib/gdatetime.c
index b5372d8346f7382a3514db748e0bd093dadcf55b..34685b5e0a8cd6e5fa6043a9e7da62978ae06c01 100644
--- a/glib/gdatetime.c
+++ b/glib/gdatetime.c
@@ -1393,12 +1393,16 @@ parse_iso8601_date (const gchar *text, gsize length,
     return FALSE;
 }
 
+/* Value returned in tz_offset is valid if and only if the function return value
+ * is non-NULL. */
 static GTimeZone *
-parse_iso8601_timezone (const gchar *text, gsize length, gssize *tz_offset)
+parse_iso8601_timezone (const gchar *text, gsize length, size_t *tz_offset)
 {
-  gint i, tz_length, offset_hours, offset_minutes;
+  size_t tz_length;
+  gint offset_hours, offset_minutes;
   gint offset_sign = 1;
   GTimeZone *tz;
+  const char *tz_start;
 
   /* UTC uses Z suffix  */
   if (length > 0 && text[length - 1] == 'Z')
@@ -1408,42 +1412,42 @@ parse_iso8601_timezone (const gchar *text, gsize length, gssize *tz_offset)
     }
 
   /* Look for '+' or '-' of offset */
-  for (i = length - 1; i >= 0; i--)
-    if (text[i] == '+' || text[i] == '-')
+  for (tz_length = 1; tz_length <= length; tz_length++)
+    if (text[length - tz_length] == '+' || text[length - tz_length] == '-')
       {
-        offset_sign = text[i] == '-' ? -1 : 1;
+        offset_sign = text[length - tz_length] == '-' ? -1 : 1;
         break;
       }
-  if (i < 0)
+  if (tz_length > length)
     return NULL;
-  tz_length = length - i;
+  tz_start = text + length - tz_length;
 
   /* +hh:mm or -hh:mm */
-  if (tz_length == 6 && text[i+3] == ':')
+  if (tz_length == 6 && tz_start[3] == ':')
     {
-      if (!get_iso8601_int (text + i + 1, 2, &offset_hours) ||
-          !get_iso8601_int (text + i + 4, 2, &offset_minutes))
+      if (!get_iso8601_int (tz_start + 1, 2, &offset_hours) ||
+          !get_iso8601_int (tz_start + 4, 2, &offset_minutes))
         return NULL;
     }
   /* +hhmm or -hhmm */
   else if (tz_length == 5)
     {
-      if (!get_iso8601_int (text + i + 1, 2, &offset_hours) ||
-          !get_iso8601_int (text + i + 3, 2, &offset_minutes))
+      if (!get_iso8601_int (tz_start + 1, 2, &offset_hours) ||
+          !get_iso8601_int (tz_start + 3, 2, &offset_minutes))
         return NULL;
     }
   /* +hh or -hh */
   else if (tz_length == 3)
     {
-      if (!get_iso8601_int (text + i + 1, 2, &offset_hours))
+      if (!get_iso8601_int (tz_start + 1, 2, &offset_hours))
         return NULL;
       offset_minutes = 0;
     }
   else
     return NULL;
 
-  *tz_offset = i;
-  tz = g_time_zone_new_identifier (text + i);
+  *tz_offset = tz_start - text;
+  tz = g_time_zone_new_identifier (tz_start);
 
   /* Double-check that the GTimeZone matches our interpretation of the timezone.
    * This can fail because our interpretation is less strict than (for example)
@@ -1462,11 +1466,11 @@ static gboolean
 parse_iso8601_time (const gchar *text, gsize length,
                     gint *hour, gint *minute, gdouble *seconds, GTimeZone **tz)
 {
-  gssize tz_offset = -1;
+  size_t tz_offset = 0;
 
   /* Check for timezone suffix */
   *tz = parse_iso8601_timezone (text, length, &tz_offset);
-  if (tz_offset >= 0)
+  if (*tz != NULL)
     length = tz_offset;
 
   /* hh:mm:ss(.sss) */
@@ -1544,7 +1548,8 @@ parse_iso8601_time (const gchar *text, gsize length,
 GDateTime *
 g_date_time_new_from_iso8601 (const gchar *text, GTimeZone *default_tz)
 {
-  gint length, date_length = -1;
+  size_t length, date_length = 0;
+  gboolean date_length_set = FALSE;
   gint hour = 0, minute = 0;
   gdouble seconds = 0.0;
   GTimeZone *tz = NULL;
@@ -1555,11 +1560,14 @@ g_date_time_new_from_iso8601 (const gchar *text, GTimeZone *default_tz)
   /* Count length of string and find date / time separator ('T', 't', or ' ') */
   for (length = 0; text[length] != '\0'; length++)
     {
-      if (date_length < 0 && (text[length] == 'T' || text[length] == 't' || text[length] == ' '))
-        date_length = length;
+      if (!date_length_set && (text[length] == 'T' || text[length] == 't' || text[length] == ' '))
+        {
+          date_length = length;
+          date_length_set = TRUE;
+        }
     }
 
-  if (date_length < 0)
+  if (!date_length_set)
     return NULL;
 
   if (!parse_iso8601_time (text + date_length + 1, length - (date_length + 1),
diff --git a/glib/gstring.c b/glib/gstring.c
index 463bfecccdc38e00e2b8fd757b45a7f9db71648f..a8386e7c125a87f783a262c2b80c2c104b76178f 100644
--- a/glib/gstring.c
+++ b/glib/gstring.c
@@ -480,8 +480,9 @@ g_string_insert_len (GString     *string,
     return string;
 
   if (len < 0)
-    len = strlen (val);
-  len_unsigned = len;
+    len_unsigned = strlen (val);
+  else
+    len_unsigned = len;
 
   if (pos < 0)
     pos_unsigned = string->len;
@@ -778,10 +779,12 @@ g_string_insert_c (GString *string,
   g_string_maybe_expand (string, 1);
 
   if (pos < 0)
-    pos = string->len;
+    pos_unsigned = string->len;
   else
-    g_return_val_if_fail ((gsize) pos <= string->len, string);
-  pos_unsigned = pos;
+    {
+      pos_unsigned = pos;
+      g_return_val_if_fail (pos_unsigned <= string->len, string);
+    }
 
   /* If not just an append, move the old stuff */
   if (pos_unsigned < string->len)
@@ -814,6 +817,7 @@ g_string_insert_unichar (GString  *string,
                          gssize    pos,
                          gunichar  wc)
 {
+  gsize pos_unsigned;
   gint charlen, first, i;
   gchar *dest;
 
@@ -855,15 +859,18 @@ g_string_insert_unichar (GString  *string,
   g_string_maybe_expand (string, charlen);
 
   if (pos < 0)
-    pos = string->len;
+    pos_unsigned = string->len;
   else
-    g_return_val_if_fail ((gsize) pos <= string->len, string);
+    {
+      pos_unsigned = pos;
+      g_return_val_if_fail (pos_unsigned <= string->len, string);
+    }
 
   /* If not just an append, move the old stuff */
-  if ((gsize) pos < string->len)
-    memmove (string->str + pos + charlen, string->str + pos, string->len - pos);
+  if (pos_unsigned < string->len)
+    memmove (string->str + pos_unsigned + charlen, string->str + pos_unsigned, string->len - pos_unsigned);
 
-  dest = string->str + pos;
+  dest = string->str + pos_unsigned;
   /* Code copied from g_unichar_to_utf() */
   for (i = charlen - 1; i > 0; --i)
     {
@@ -921,6 +928,7 @@ g_string_overwrite_len (GString     *string,
                         const gchar *val,
                         gssize       len)
 {
+  gsize len_unsigned;
   gsize end;
 
   g_return_val_if_fail (string != NULL, NULL);
@@ -932,14 +940,16 @@ g_string_overwrite_len (GString     *string,
   g_return_val_if_fail (pos <= string->len, string);
 
   if (len < 0)
-    len = strlen (val);
+    len_unsigned = strlen (val);
+  else
+    len_unsigned = len;
 
-  end = pos + len;
+  end = pos + len_unsigned;
 
   if (end > string->len)
     g_string_maybe_expand (string, end - string->len);
 
-  memcpy (string->str + pos, val, len);
+  memcpy (string->str + pos, val, len_unsigned);
 
   if (end > string->len)
     {
diff --git a/glib/tests/gdatetime.c b/glib/tests/gdatetime.c
index d46f653acb4370dc73e0310cfc7112f5f2f84123..15eb81cf1edd388604d94cd5d89c5bcbd45892e4 100644
--- a/glib/tests/gdatetime.c
+++ b/glib/tests/gdatetime.c
@@ -866,6 +866,23 @@ test_GDateTime_new_from_iso8601 (void)
    * NaN */
   dt = g_date_time_new_from_iso8601 ("0005306 000001,666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666600080000-00", NULL);
   g_assert_null (dt);
+
+  /* Various invalid timezone offsets which look like they could be in
+   * `+hh:mm`, `-hh:mm`, `+hhmm`, `-hhmm`, `+hh` or `-hh` format */
+  dt = g_date_time_new_from_iso8601 ("2025-02-18T18:14:00+01:xx", NULL);
+  g_assert_null (dt);
+  dt = g_date_time_new_from_iso8601 ("2025-02-18T18:14:00+xx:00", NULL);
+  g_assert_null (dt);
+  dt = g_date_time_new_from_iso8601 ("2025-02-18T18:14:00+xx:xx", NULL);
+  g_assert_null (dt);
+  dt = g_date_time_new_from_iso8601 ("2025-02-18T18:14:00+01xx", NULL);
+  g_assert_null (dt);
+  dt = g_date_time_new_from_iso8601 ("2025-02-18T18:14:00+xx00", NULL);
+  g_assert_null (dt);
+  dt = g_date_time_new_from_iso8601 ("2025-02-18T18:14:00+xxxx", NULL);
+  g_assert_null (dt);
+  dt = g_date_time_new_from_iso8601 ("2025-02-18T18:14:00+xx", NULL);
+  g_assert_null (dt);
 }
 
 typedef struct {