A spoofing vulnerability exists when a Skype for Business Server does not properly sanitize a specially crafted request. An authenticated attacker could exploit the vulnerability by sending a specially crafted request to an affected server. The attacker who successfully exploited this vulnerability could then perform cross-site scripting attacks on affected systems and run scripts in the security context of the current user.
For the vulnerability to be exploited, a user must click a specially crafted URL that takes the user to a targeted Skype for Business site.
In an email attack scenario, an attacker could exploit the vulnerability by sending an email message containing the specially crafted URL to the user of the targeted Skype for Business site and convincing the user to click the specially crafted URL.
The security update addresses the vulnerability by helping to ensure that Skype for Business Server properly sanitizes web requests.
## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Microsoft | Skype for Business Server 2019 CU2 | | [KB4534761](https://patchblox.com/security/data/fix/microsoft/kb4534761.md) | Dec 10, 2019 | --- Data as of 2026-11-07T18:46:35Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo Free to use with attribution: show "Data: Patchblox Patch Radar" with a link to https://patchblox.com/security/patch-radar. Terms, including what needs a written agreement: https://patchblox.com/security/patch-radar/use-the-data Product names, logos and trademarks shown on Patch Radar belong to their respective owners. They are used only to identify the software each security fix applies to and to help readers find their platform. Their use does not imply any affiliation with, or endorsement by, those owners, and Patchblox is not affiliated with any of them.