Ember.js Potential XSS Exploit With User-Supplied Data When Binding Primitive Values

In general, Ember.js escapes or strips any user-supplied content before
inserting it in strings that will be sent to innerHTML. However, we have
identified a vulnerability that could lead to unescaped content being inserted
into the innerHTML string without being sanitized.

When a primitive value is used as the Handlebars context, that value is not
properly escaped. An example of this would be using the {{each}} helper to
iterate over an array of user-supplied strings and using {{this}} inside the
block to display each string.

In applications that contain templates whose context is a primitive value and
use the {{this}} keyword to display that value, a specially-crafted payload
could execute arbitrary JavaScript in the context of the current domain
(“XSS”).

This vulnerability affects applications that contain templates whose context is
set to a user-supplied primitive value (such as a string or number) and also
contain the {{this}} special Handlebars variable to display the value.