is rendered by the web browser, to ensure the expected advertising elements are present. Detection is simplified since the extension is not yet capable of replacing content; Loopback proxies provide this additional functionality. These methods do not detect the presence of the Adblock Plus extension directly, only the effects of the filters. They are vulnerable to continued filter updates, and whitelist-filtering web scripts with extensions such as NoScript. An attempt was made to detect the plug-in itself, but that detection method was rendered unusable by the 0.7.5.2 update of Adblock Plus. Google Chrome had a defect in Content Security Policy that allowed the detection of any installed extension, including Adblock Plus for Google Chrome. The solution for this issue arrived in Google Chrome 18, and required each developer to make changes to their extensions. Adblock Plus for Google Chrome fixed this in version 1.3. Security Starting with Adblock Plus 3.2 for Chrome, Firefox and Opera, the Adblock Plus filter syntax allowed filter lists to execute arbitrary code in the context of certain kinds of web pages via the $rewrite filter option. This feature could be used by list maintainers to fix bugs in web pages caused by ad blocking or to circumvent ad blocker detection, but also could be abused by malicious filter rules. This issue was not unique to Adblock Plus and affected all extensions that offered such functionality. By contrast, uBlock Origin did not support this functionality and required all such scripts to pass a manual verification by the uBlock Origin maintainers. The issue was fixed in Adblock Plus 3.5.2 for Chrome, Firefox and Opera. Controversies Controversy over ad filtering and ad whitelisting The owners of some websites which use third-party hosted online advertising to fund the hosting of their websites have argued that the use of ad-blocking software such as Adblock Plus risks cutting off their revenue stream. While some websites such as The New York Times and The Daily Telegraph have successfully implemented subscription and membership-based paywall systems for revenue, many websites today rely on third-party hosted online advertising to function. On December 5, 2011, Wladimir Palant announced that certain "acceptable" ads would be whitelisted in upcoming builds of the Adblock Plus software, with the option to remove whitelisted ads by using a custom setting in the software. According to Palant, only static advertisements with a maximum of one script will be permitted as "acceptable", with