https://www.sci.news/space/bepicolombo-oxygen-carbon-ions-magnetosphere-venus-12856.html
In August 2021, the ESA/JAXA Mercury-bound BepiColombo spacecraft performed its second flyby of Venus and provided a short-lived observation of its induced magnetosphere.
In this case, the carbon and oxygen are coming from a much more mundane source: the solar wind.
When high-energy particles from the solar wind collide with molecules in Venus' upper atmosphere, they carry enough energy to break some of those molecules into their constituent atoms. Since the Venusian atmosphere is almost entirely CO2, you should expect this process to generate C and O ions — which is exactly what we've now observed!
If life is proven to exist on Venus, it would be really exciting. Besides the obvious reason to be excited there's also my thought: If in this planetary system two planets out of 98 have life on them, then that would mean that life isn't as rare as we conceived it to be.
Edit: Had the tab open for a while without refreshing before posting, so I didn't see the comment that says it's just solar wind. :(