WebDyne versions from 2.031 before 3.022 for Perl execute files with .psp anywhere in the name as Perl pages.
WebDyne decides whether to run a requested file as a page by matching its name against WEBDYNE_PSP_EXT_RE, which has no end anchor.
An application that accepts uploads by checking only the final extension lets a remote attacker upload a file such as report.psp.pdf and run its embedded Perl by requesting it.
Upgrade to WebDyne 3.022 or later.