system/HTTP/ContentSecurityPolicy.php
public function addBaseURI($uri, ?bool $explicitReporting = null)
	{
		$this->addOption($uri, 'baseURI', $explicitReporting ?? $this->reportOnly);

		return $this;
	}
public function addBaseURI($uri, ?bool $explicitReporting = null)
	{
		$this->addOption($uri, 'baseURI', $explicitReporting ?? $this->reportOnly);

		return $this;
	}
Adds a new base_uri value. Can be either a URI class or a simple string.

base_uri restricts the URLs that can appear in a page’s <base> element.

@see http://www.w3.org/TR/CSP/#directive-base-uri

@param string|array $uri
@param boolean|null $explicitReporting

@return $this