Security researcher Tyson Smith and Jesse Schwartzentruber of the BlackBerry Security Automated Analysis Team used the Address Sanitizer tool while fuzzing to discover an out-of-bounds read during polygon rendering in MathML. This can allow web content to potentially read protected memory addresses. In combination with previous techniques used for SVG timing attacks, this could allow for text values to be read across domains, leading to information disclosure.
In general this flaw cannot be exploited through email in the Thunderbird and Seamonkey products because scripting is disabled, but is potentially a risk in browser or browser-like contexts.