Serialized objects can be altered outside of any Java program unless they are protected using mechanisms such as sealing and signing. (See guideline ENV01-J. Place all security-sensitive code in a single JAR and sign and seal it.) If an object referring to a system resource becomes serialized, and an attacker can alter the serialized form of the object, it becomes possible to modify the system resource that the serialized handle refers to. For example, an attacker may modify a serialized file handle to refer to an arbitrary file on the system. In the absence of a security manager, any operations that use the file handle will be carried out using the attacker-supplied file path and file name.
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