Language: TypeScript
Label: safe
CWE: CWE-79 \u2014 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

Code:
export const isLocalLink = (link: string | null) => {
  return !!(link?.includes(location.origin) || link?.startsWith("/"));
};