Strange apache-error with wp-settings include /category.php -> /categorx.php

hi everyone,

yesterday we got an mysterious error in the apache error log:
[…] [error] […] sapi_apache2.c(326): [client …] [remote: ..] PHP Warning: require(…/wp-includes/categorx.php): failed to open stream: No such file or directory in …/wp-settings.php on line 175

as a clear result this, the webserver generates http 500 errors

mysterious cause of the following:
– at this time there was no user logged an the server via ssh or sftp. nobody changed the wp-setting.php file. (checked in the logfiles)
– while the error persists, in the wp-setting.php file has the correct include /category.php on line 175
– our setting is a loadblancer which distributes to serveral webserver. all webserver have the same nfs-share volume for the webroot. BUT only one server wants to include the /categorx.php file
– we reinstalled the complete wordpress, but the error persists
– the ids shows no hacking attack
– no other logs shows something unusual

after this we restart the apache service and the and the error was fixed, but it is a bad feeling not to know what happend.

Did anybody else had sucha strange behaviour of his webserver?

br
marc

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