(0Day) Microsoft SharePoint Calendar Overlay Hyperlink Injection Vulnerability
Vulnerability Details
This vulnerability allows remote attackers to inject unexpected hyperlinks on affected installations of Microsoft SharePoint. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file.
The specific flaw exists within the implementation of calendar overlays. The issue results from the lack of proper validation of user-supplied data, which can lead to the injection of an arbitrary hyperlink. An attacker can leverage this vulnerability to redirect a target user to a deceptive, untrusted page.
Additional Details
08/28/25 - ZDI reported the vulnerability to the vendor
08/29/25 – the vendor acknowledged the receipt of the report
09/25/25 – the vendor communicated that the reported behavior did not meet the bar for immediate servicing
11/26/25 – ZDI notified the vendor of the intention to publish the cases as a 0-day advisory on 12/10/25
-- Mitigation: Given the nature of the vulnerability, the only salient mitigation strategy is to restrict interaction with the product
Disclosure Timeline
- 2025-08-28 - Vulnerability reported to vendor
- 2025-12-10 - Coordinated public release of advisory
- 2025-12-10 - Advisory Updated
Credit
Vladislav Berghici of Trend Research
