A zero-day cross-site scripting (XSS) flaw that has been exploited in the wild has now been patched for Zimbra Collaboration Suite in version 8.8.15 patch 41. Two other vulnerabilities have been patched in this update, which are a high severity flaw that can allow for denial of service (DoS) attacks, and another vulnerability that can cause the exposure of JSP and XML files. The patches for these other two flaws are also included in version 9.0.0 patch 34, and the latest update released, version 10.0.2. Zimbra Collaboration Suite (ZCS) is an email platform and web client with both a network and an open-source edition. Links to download the latest version for both the network and open-source edition of ZCS is provided within the Security Advisory Wiki released by Zimbra, along with a summary of vulnerability information including severity and CVSS score. 

 The exploited XSS flaw, CVE-2023-37580, was identified in early July, however administrators were required to apply the fix manually, as specified in the security update released at the time. This flaw occurs in the Zimbra Web Client, and exploitation could result in attackers obtaining sensitive information from the vulnerable systems, or being able to execute arbitrary code. This vulnerability is resolved through the inclusion of the escapeXml() function in the mailbox parameters. This function sanitises data input by users and escapes special characters used in XML markups, which results in prevention of XSS attacks. It was not revealed that this flaw was actively exploited when this manual fix was first suggested, so it is possible this update would have been regarded as of lower importance than was true. The US Cybersecurity and Infrastructure Security Agency (CISA) have now added this vulnerability to their Known Exploited Vulnerabilities Catalog, confirming it’s exploitation and severity, and encouraging agencies and businesses to apply the relevant updates to fix this flaw as soon as possible.  

 The other two vulnerabilities patched in the recent updates are CVE-2023-0464 and CVE-2023-38750. CVE-2023-0464 is an Open-SSL flaw that affects the policy constraints when verification of X.509 certificate chains is performed. Attackers can exploit this flaw through the use of a malicious certificate chain which uses up computational resources. This results in a DoS attack on the target system. This vulnerability has been given a high severity rating and a CVSS base score of 7.5. CVE-2023-38750 is a vulnerability that can be exploited in order to expose the internal JSP and XML files of the vulnerable systems. Both of these flaws are resolved in all three recent updates for ZCS, further information about additional content and fixes in each release version can be found in the Zimbra Security Centre. Users should apply the most suitable update for their systems as soon as possible in order to mitigate these three flaws.