The attacker is sequentially changing the serviceID parameter in the URL, likely in an attempt to access objects that they are not authorized to see. This is indicative of an attempt to exploit an Insecure Direct Object Reference (IDOR) vulnerability, where unauthorized access to objects can occur by manipulating input or changing parameters in the URL.
An insecure direct object reference (IDOR) vulnerability occurs when an application exposes a reference to an internal object, such as a file, directory, database record, or key, without any proper authorization or validation mechanism. This allows an attacker to manipulate the reference and access other objects that they are not authorized to access. In this case, the attacker was trying to exploit the IDOR vulnerability in the servicestatus.php script, which accepts a serviceID parameter that directly references a service object. By changing the value of the serviceID parameter, the attacker could access different services that they were not supposed to see. References: The Official CompTIA PenTest+ Student Guide (Exam PT0-002) eBook, Chapter 4, Section 4.2.2: Insecure Direct Object References; Best PenTest+ certification study resources and training materials, Section 1: Cross-site Scripting (XSS) Attack.