Failed to sanitize html because the input is unstable
This error occurs when $sanitize sanitizer tries to check the input for possible mXSS payload and the verification
errors due to the input mutating indefinitely. This could be a sign that the payload contains code exploiting an mXSS
vulnerability in the browser.
mXSS attack exploit browser bugs that cause some browsers parse a certain html strings into DOM, which once serialized doesn't match the original input. These browser bugs can be exploited by attackers to create payload which looks harmless to sanitizers, but due to mutations caused by the browser are turned into dangerous code once processed after sanitization.