Core:
    Fixed bug #81518 (Header injection via default_mimetype / default_charset).
Date:
    Fixed bug #81500 (Interval serialization regression since 7.3.14 / 7.4.2).
DBA:
    Fixed bug #81588 (TokyoCabinet driver leaks memory).
MBString:
    Fixed bug #76167 (mbstring may use pointer from some previous request).
Opcache:
    Fixed bug #81512 (Unexpected behavior with arrays and JIT).
PCRE:
    Fixed bug #81424 (PCRE2 10.35 JIT performance regression).
XML:
    Fixed bug #79971 (special character is breaking the path in xml function). (CVE-2021-21707)
XMLReader:
    Fixed bug #81521 (XMLReader::getParserProperty may throw with a valid property).