Critical. A vulnerability whose exploitation could allow code execution without user interaction. These scenarios include self-propagating malware (e.g. network worms), or unavoidable common use scenarios where code execution occurs without warnings or prompts. This could mean browsing to a web page or opening email.
A strain is a stretching or tearing of muscle or tendon. A tendon is a fibrous cord of tissue that connects muscles to bones. Strains often occur in the lower back and in the hamstring muscle in the back of your thigh. Initial treatment for both sprains and strains includes rest, ice, compression and elevation.
Not to be confused with Sprain. A strain is an injury to a muscle in which the muscle fibers tear as a result of overstretching. A strain is also colloquially known as a pulled muscle or torn muscle. The equivalent injury to a ligament is a sprain.