[exim] Unable to read domainkey file

Hi list!

Since yesterday I cannot read the domainkey file by sending the E-Mails.
In the log I see:

2021-03-20 08:41:28 1lNWEh-0004NA-PE Tainted filename
'/etc/exim/domainKeys/lucabert.de/2021.priv'

2021-03-20 08:41:28 1lNWEh-0004NA-PE unable to open file for reading:
/etc/exim/domainKeys/lucabert.de/2021.priv


Of course the whole path is readable for the user "exim".
Yesterday I updated the system to Debian 10 and recompiled Exim to the
latest Version 4.94.

Do someone has any idea what can be the problem?

Thanks
Luca Bertoncello
(lucabert@???)