What are the causes of Bleeding of the stool and it can be Cancerous? Or even Dangerous?

Bleeding can occur along any part of the gastrointestinal tract from the mouth to the anusit appears either from the mouth or in the stool, or in vomit, and can be hidden and detectable by tests.Bleeding in the digestive tract may be worsened by another bleeding disorder.
Possible symptoms include blood passing black tarry stools (hematemesis) this results from bleeding high up in the digestive tract.
This could be a case of hemorrhoids, which are swollen tissue that contain veins and are located in the wall of the rectum and anus.Hemorrhoids become inflammed and develope a blood clot either bleed or become enlarged and protrude,there are two types,internal hemorrhoids and external hemorrhoids.When a person strains to hard several times to release the stool hemorrhoids can occur(straing along with constipation).
Hemorrhoids can bleed after a bowel movement occurs producing blood streaked stools or leaving blood on the TP.
Polyps are a growth of tissue from the intestinal wall that protrude into the intestine and is usually non cancerous.These may grow with or with out stalks and vary considerably in size.Commonly found in the rectum growing, or in the lower portion of the large intestine.The biggest issues with these it they can become canaous if left alone and not removed.These can cause blood from the back side as well.A endoscopy may be in order to find the cause.

Google haemorrhoids. Most people have them some time in their life.

Could be anything. What colour is the blood? If bright red, it's at the end of the GI tract meaning it's probably a fissure or haemorrhoids.