There is a news story published http://www.zdnet.com/article/cia-has-been-hacking-into-wi-fi-routers-for-years-leaked-documents-show/ about documents from wikileaks on the CIA. The document lists various makes and models of routers that they have exploits for. They mention DDWRT and Tomato firmware but I didn’t see openwrt mentioned.
It appears that in order to implant their exploit that have to sneak into your home or business when you aren’t around. It also appears that this exploit is targeting Americans. Perhaps they do something different elsewhere. They also take great pains so that the target can’t tell their firmware has been replaced.
You can’t really protect yourself from people that sneak into your house and mess with your computers but it is interesting to think about.