$\ce{CO_x}$ are part of the oxocarbon molecule class. Commonly known are $\ce{CO}$ and $\ce{CO2}.$ However, there are molecules in which $x$ is equal to or larger than $3.$ Those molecules are barely known, other than the fact that they're unstable.
$\ce{CO3}$ decomposes slowly enough that it may come into contact with other molecules (including biomolecules), but nothing is known of its possible oxidizing potential.
$\ce{CO4},$ $\ce{CO5}$ and $\ce{CO6}$ are very unstable, and could possibly be strong oxidants (though it may never be known since they're too unstable).
Other than that, any information?