CVE-2024-28867: Un-sanitized metric name or labels can be used to take over exported metrics

In code which applies un-sanitized string values into metric names or labels, like this:

let lang = try? request.query-get(String.self, at: "lang")
Counter (
label: "language",
dimensions: [("lang", lang ?? "unknown" )]
)

an attacker could make use of this and send a ?lang query parameter containing newlines, } or similar characters which can lead to the attacker taking over the exported format – including creating unbounded numbers of stored metrics, inflating server memory usage, or causing “bogus” metrics.