OpenDMARC through 1.3.2 and 1.4.x allows attacks that inject authentication results to provide false information about the domain that originated an e-mail message. This is caused by incorrect parsing and interpretation of SPF/DKIM authentication results, as demonstrated by the example.net(.example.com substring.
https://www.usenix.org/system/files/sec20fall_chen-jianjun_prepub_0.pdf
https://sourceforge.net/p/opendmarc/tickets/237/
https://lists.debian.org/debian-lts-announce/2023/08/msg00035.html