Image forming apparatus and authentication method executed by the same

An image forming apparatus in which an authentication method for executing a print job is selected, the authentication method including a first method and a second method, the first method being a method in which a password is inputted, and the second method being a method in which a second specific word is inputted, the image forming apparatus comprising:

• an operation panel;
• and
• a controller, wherein
• the controller includes a processor and storage,
• the storage stores a control program therein,
• the processor functions as a first reception section, an extraction section, a second reception section, and a determining section through execution of the control program,
• the first reception section receives a print job for a document from an external terminal device,
• the extraction section extracts a first specific word from an updated portion in the document, the updated portion being specified by update history information,
• the second reception section receives input of the second specific word through the operation panel,
• the determining section determines whether or not to permit execution of the print job according to whether or not the second specific word matches the first specific word, and
• when the determining section determines to permit the execution of the print job, the image forming apparatus executes the print job.