WordPress 5.7.1 Patches XXE Flaw in PHP 8

WordPress has released version 5.7.1 of its popular content management system (CMS), which brings more than 25 bug fixes, including patches for two security vulnerabilities.

One of the patched security flaws is an XML External Entity (XXE) vulnerability in the ID3 library in PHP 8, which is used by WordPress. Tracked as CVE-2021-29447, the vulnerability is considered high severity.

Designed to parse ID3 tags from MP3 audio files, the library did not explicitly disable XML entities in PHP 8, which rendered WordPress 5.7 and older versions vulnerable to XXE attacks via MP3 file uploads.

The issue was introduced in August 2020 and could be exploited by any user who has the ability to upload files. Only WordPress deployments that use PHP 8 (0.3%) are affected, so the vast majority of websites are safe from exploitation attempts of this vulnerability.

The bug was reported by code quality and security provider SonarSource, which last year acquired code security testing company RIPS Technologies, which also specializes in PHP code testing.

Affecting the REST API, the second vulnerability could be exploited to access sensitive data. Tracked as CVE-2021-29450 and reported by Mikael Korpela, the security bug is considered medium severity.

[ Related Webinar May 19th: API MythBusters – The Five Myths Putting you at Risk ]

The issue, WordPress explains, exists in a block in the WordPress editor, which could be exploited by attackers to expose password-protected posts and pages. Successful exploitation of the flaw requires for the attacker to have at least contributor privileges.

To further improve the security of WordPress, its developers are considering treating Google’s Federated Learning of Cohorts (FLoC) as a security threat and automatically blocking it on websites.

Meant as a replacement for third-party cookies, FLoC brings into the mix interest-based advertising, where users are placed into large groups based on their interests, thus providing businesses with new ways to target them with their ads.

While FLoC is more private than cookies, it does have its own privacy implications, including the fact that users are being tracked and data on their browsing habits is being shared with third-parties. WordPress is powering nearly half of the websites out there, and its developers are looking at FLoC as a possible security concern when it comes to users’ privacy.

WordPress, however, is not the only Internet entity to view FLoC as a potential privacy threat. While Google is including the feature in Chrome, other browser vendors have not adopted it.

In an advisory on Friday, the Cybersecurity and Infrastructure Security Agency (CISA) warned that the vulnerabilities addressed in WordPress 5.7.1 affect versions 4.7 to 5.7 and that attackers able to successfully exploit one of these could take control of an affected website.

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Ionut Arghire is an international correspondent for SecurityWeek.

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