As artificial intelligence (AI) and chatbot technologies like ChatGPT continue to evolve, educators grapple with the risks and benefits these advances bring to online assessment. The democratisation of AI-based technologies, while offering personalised learning experiences, threatens online assessment legitimacy and academic integrity. This paper critically examines the intersection of AI chatbots and online assessments, in the context of their impact on the design of authentic online assessments. The widespread usage of AI chatbots has caused serious problems for the validity of online tests because of the possibility of student abuse. This underlines the need for 'authentic assessments' that concentrate on higher-order cognitive skills, problem-solving, creative thinking, and collaborative talents and calls for a reevaluation of conventional assessment methods. These types of assessments not only align with the evolving pedagogical needs of the 21st century but also present tasks that are significantly challenging for AI chatbots to replicate, thereby preserving their integrity. Conversely, the paper also explores how AI can facilitate the assessment process by automating certain tasks, providing personalised learning experiences, and supporting collaborative assessments. The era of AI chatbots presents an opportunity to rethink and enhance online assessments, making them more authentic, meaningful, and resistant to AI-assisted malpractice.