The chartjs WordPress plugin through 2023.2 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).

The chartjs WordPress plugin through 2023.2 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).

This affects the package chart.js before 2.9.4. The options parameter is not properly sanitized when it is processed. When the options are processed, the existing options (or the defaults options) are deeply merged with provided options. However, during this operation, the keys of the object being set are not checked, leading to a prototype pollution.