Why is Splunk reporting possible typos in configuration file stanzas after upgrading to 4.2?

Splunk 4.2 checks the keys (only keys, not values!) in live configuration files by comparing them with the contents of the spec file for that configuration file.

For example, let's say that I create the following stanza in $SPLUNK_HOME/etc/system/local/inputs.conf :

[monitor:///var/log/kludgy.log]
sourcetype = kludgy
crcPepper = <SOURCE>

On splunkd startup, there will be a syntax check for the "crcPepper" configuration key performed against the keys listed for the [monitor://] stanza type in $SPLUNK_HOME/etc/system/README/inputs.conf.spec - http://www.splunk.com/base/Documentation/latest/Admin/Inputsconf :

[monitor://<path>]
* This directs Splunk to watch all files in <path>. 
* <path> can be an entire directory or just a single file.
* You must specify the input type and then the path, so put three slashes in your path if you're starting 
at the root (to include the slash that goes before the root directory).

# Additional attributes:

host_regex = <regular expression>
* If specified, <regular expression> extracts host from the filename of each input file.

(...)

_blacklist = ...
* This setting is deprecated.  It is still honored, unless "blacklist" attribute also exists.
dedicatedFD = ...
* This setting has been removed.  It is no longer needed.

As you can imagine, the "crcPepper" key will not be found here which will cause Splunk to report the error on the standard output when splunkd is started from the command line :

Checking conf files for typos...
Possible typo in stanza [monitor:///var/log/kludgy.log] in /home/octavio/splunk/etc/system/local/inputs.conf, line 6: crcPepper  =  <SOURCE>

Note that this only a warning, Splunk does not take any action other than reporting this possible syntax error.