There is functionality in the Store Locator Plus for WordPress plugin through 5.5.14 that made it possible for authenticated users to update their user meta data to become an administrator on any site using the plugin.
[
{
"product": "Store Locator Plus for WordPress",
"vendor": "Store Locator Plus",
"versions": [
{
"lessThanOrEqual": "5.5.14",
"status": "affected",
"version": "5.5.14",
"versionType": "custom"
}
]
}
]