The Two Most Common Web Bugs, XSS and IDOR, and Why Google Pays Them Differently
XSS happens when a site puts user input into a page unchanged, so another person's browser runs it as code; the fix is escaping on output. IDOR happens when a server hands over whatever id it is asked for without checking the record is yours; the fix is an ownership check on the server. Google's table puts XSS under 'execute code on the client' (C0), $10,000 base on a standard Google app, and IDOR under logic flaws (S2), priced by how sensitive the exposed data is: on the same standard Google app, $3,133.7 to $31,337.