[camgunz]

They run this down as best they can (TLDR they don't think the skills have enough information about their personas to target ads to them, therefore Amazon must be doing the targeting, but they can't 100% rule it out):

> In contrast, skills can only rely on persona’s email address, if allowed permission, IP address, if skills con- tact non-Amazon web services, and Amazon’s cookies, if Amazon collaborates with the skills, as unique identifiers to reach to personas. Though we allow skills to access email address, we do not log in to any online services (except for Amazon), thus skills cannot use email addresses to target personalized ads. Skills that contact non-Amazon web services and skills that collaborate with Amazon can still target ads to users. However, we note that only a handful (9) of skills contact few (12) advertising and tracking services (Table 1 and Figure 2), which cannot lead to mass targeting. Similarly, we note that none of the skills re-target ads to personas (Section 5.3), which implies that Amazon might not be engaging in data sharing partnerships with skills. Despite these observations, we still cannot rule out skills involvement in targeting of personalized ads.