The Mozilla Foundation has undertaken the heady process of scoring several major streaming services on their displays of political ads, including CBS All Access. CBS All Access performed broadly in the middle of the pack, compared to the other services in the study: Hulu, Roku, tubi, YouTube TV, and Sling.

Let’s look first at the study itself, and then CBS All Access’s scores.

The six services in the study were all what Mozilla calls “popular streaming platforms”. Each of them has at least one tier that’s ad-supported, where viewers are shown commercials either before, during, or after the content they’re watching. In the course of the study, each service was rated on five metrics:

1. Policies around political ads - namely, do they have one? Services who performed well here (like CBS All Access) had clear policies in place around things like vetting political ads and clear disclosures when displaying ads. Services who performed poorly had fewer policies or outsourced the decisions about political ads to a third party.

2. Ad transparency - can the public access information about who has been placing ads, and what ads they’ve been placing? The best performer here, YouTube TV, voluntarily reports ad spend and has a public-facing library of political ads. The worst performers (of which CBS All Access is one) has no public information about political ads.

3. Ad targeting - broadly, this one is a measure of how invasive the service’s ad targeting is into your personal information. Hulu and YouTube TV performed the best here, but on both services, the protections they have in place only extend to what’s identified as election ads, and might not protect you from special interests with political motivations.

4. Potential abuse - how robust is the service’s system for ensuring that they can’t be gamed by rogue actors? Most services scored a moderate grade here, with the exception of Sling, who had marks taken away because of the opacity of their third-party self-service ad platform.

5. User control - how much control do you, as a viewer, have to check how many political messages you get served? Only YouTube TV got some credit here, since Google (who owns YouTube) allows you to see your own ad categories and delete your data.

So how does CBS All Access stack up? In overall scores, CBS All Access got a “C”. That puts it right in the middle of the pack. From best to worst:

• YouTube TV scored a “B” (the only one to do so)

• CBS All Access and Hulu scored “C”s

• Roku and tubi scored “D”s

• Sling scored a sound “F”

Within the overall results, CBS All Access was a mixed bag. They scored points for their strong political ad policies, middle of the road for ad targeting and potential for abuse, and poorly for ad transparency and user control (both measures, it should be noted, were scored poorly among all the services).

Overall, here’s what Mozilla had to say about CBS All Access: “CBS seems to have strong policies in place aimed at vetting political ads and preventing platform abuse, enforcing rules similar to those it applies to broadcast television. However, the platform does not provide comprehensive ad transparency tools to enable researchers to ensure the integrity of the platform.”

To read the entire study for yourself, including details on the scores and the other things the Mozilla Foundation is doing to promote a healthier internet, head to foundation.mozilla.org.