firefox: thunderbird: expat: libexpat in Expat allows attackers to trigger large dynamic memory allocations via a small document that is submitted for parsing

A memory amplification vulnerability in libexpat allows attackers to trigger excessive dynamic memory allocations by submitting specially crafted XML input. A small input 250 KiB can cause the parser to allocate hundreds of megabytes, leading to denial-of-service DoS through memory exhaustion...