Starting yesterday i'm suddenly seeing all draw.io embedded diagrams in dark mode, which is indeed my MacOS Ventura system theme but up until now all Confluence content was presented in light theme... including the draw.io editor itself (which is still light themed, only the embedded diagrams are affected).
I'm Confluence admin and verified we do not have any draw.io Confluence app configuration setup (also wouldn't want to enforce any theme/setting on all users).