CONTENT-MODIFICATION SYSTEM WITH FEATURE FOR CONTROLLING VIEWER EXPOSURE TO SPOILERS IN ADVERTISEMENTS

In one aspect, a method includes receiving a request for supplemental content for use by a content-presentation device in performing a content-modification operation relative to a modifiable content-segment that the content-presentation device is scheduled to receive. The method also includes determining that the modifiable content-segment comprises a promotional advertisement for a content series. The method also includes identifying content that the promotional advertisement spoils from the content series. The method also includes based on historical content consumption data associated with the content-presentation device, determining that the content-presentation device has presented less than a predefined threshold amount of the identified content. The method also includes in response to determining that the content-presentation device has presented less than the predefined threshold amount of the identified content, performing an action that facilitates the content-presentation device replacing the modifiable content-segment with supplemental content.