Over the last few years, big brands and small businesses have adopted social media into their marketing strategy. One of the key features that Facebook pages offer these brands is ability to have multiple administrators for a page. These administrators are granted access through their personal Facebook accounts. Therefore, it is likely that whomever obtained access to the Walmart Careers page did so by compromising an administrator’s Facebook account.
FireSheep - This is a free Firefox extension that gives users the ability to hijack unencrypted sessions on public WiFi networks. It is possible that an administrator of this page was browsing Facebook without HTTPS enabled on a public WiFi network, such as a Starbucks. A scammer may have been sitting on the network and discovered this account was tied to the Walmart careers page.
The Walmart Careers page also offers an email employment newsletter, for which you can sign up to receive up-to-date career information in your inbox.