Due to a missing case handling object types, a type confusion vulnerability could occur, resulting in a crash. We presume that with enough effort that it could be exploited to run arbitrary code. This vulnerability affects Firefox ESR < 68.4 and Firefox < 72.
The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.