Merge branch 'PHP-7.3' into PHP-7.4

* PHP-7.3:
  Yet another check for php_strip_tags_ex()

Author: cmb69

ext/standard/string.c

@@ -5380,7 +5380,7 @@ PHPAPI size_t php_strip_tags_ex(char *rbuf, size_t len, uint8_t *stateptr, const
 			break;
 		case '"':
 		case '\'':
-			if (*(p-1) != '\\') {
+			if (p >= buf + 1 && *(p-1) != '\\') {
 				if (lc == c) {
 					lc = '\0';
 				} else if (lc != '\\') {