PHP 5.6.20 has been released 31 Mar 2016. It seems we're a bit late compared to the usual upgrade rhythm to upgrade our Docker images.
Fixed bug #71527 (Buffer over-write in finfo_open with malformed magic file).
Fixed bug #71906 (AddressSanitizer: negative-size-param (-1) in mbfl_strcut).
Fixed bug #71860 (Invalid memory write in phar on filename with \0 in name).
Fixed bug #71704 (php_snmp_error() Format String Vulnerability).
Fixed bug #71798 (Integer Overflow in php_raw_url_encode).