+12. [POSSIBLE CONFIG BREAKAGE] ALT_CONFIG_ROOT_ONLY is no longer optional and
+ is forced on. This is mitigated by the new build option
+ TRUSTED_CONFIG_PREFIX_LIST which defines a list of pathname prefices which
+ are trusted; if a config file is owned by root and is under that prefix,
+ then it may be used by the Exim run-time user.
+
+13. [POSSIBLE CONFIG BREAKAGE] The Exim user is no longer automatically
+ trusted to supply -D<Macro[=Value]> overrides on the command-line. Going
+ forward, we recommend using TRUSTED_CONFIG_PREFIX_LIST with shim configs
+ that include the main config. As a transition mechanism, we are
+ temporarily providing a work-around: the new build option
+ WHITELIST_D_MACROS provides a colon-separated list of macro names which
+ may be overriden by the Exim run-time user. The values of these macros
+ are constrained to the regex ^[A-Za-z0-9_/.-]*$ (which explicitly does
+ allow for empty values).
+