This affects all versions of package mout. The deepFillIn function can be used to 'fill missing properties recursively', while the deepMixIn 'mixes objects into the target object, recursively mixing existing child objects as well'. In both cases, the key used to access the target object recursively is not checked, leading to a Prototype Pollution.
This affects the package express-fileupload before 1.1.8. If the parseNested option is enabled, sending a corrupt HTTP request can lead to denial of service or arbitrary code execution.