Security readout for executives and security teams
Plain-English summary
CVE-2020-1099 is a Microsoft SharePoint cross-site scripting issue. An attacker with low privileges could send a specially crafted request that may cause script execution in another user’s browser after interaction. Business impact is mainly limited data exposure or unauthorized actions within the victim’s SharePoint context, not server takeover.
Executive priority
Handle as a routine but important SharePoint security update. It is not described as actively exploited in the provided sources, but collaboration platforms often hold sensitive business data and have many authenticated users, so exposed deployments should not wait for a broad patch cycle.
Technical view
The flaw is CWE-79 in Microsoft SharePoint Enterprise Server 2016 and SharePoint Server 2019. SharePoint does not properly sanitize a specially crafted web request. CVSS 3.1 is 5.4 with network access, low complexity, low privileges, required user interaction, changed scope, low confidentiality and integrity impact, and no availability impact.
Likely exposure
Exposure is limited to organizations running Microsoft SharePoint Enterprise Server 2016 or SharePoint Server 2019. Risk is higher for internet-facing or broadly accessible SharePoint deployments, especially where many authenticated users can submit content or requests that other users may view.
Exploitation context
The provided sources do not show CISA KEV listing or active exploitation. The CVSS vector indicates an attacker needs low privileges and victim interaction. Treat exploitability as plausible for exposed SharePoint environments, but do not assume active exploitation from this bundle alone.
Researcher notes
Evidence is limited to CVE, CVE List, and MSRC references. The bundle does not include exploit proof, affected build ranges, or named mitigations beyond vendor advisory direction. CVE-2020-1099 is distinct from CVE-2020-1100, CVE-2020-1101, and CVE-2020-1106.
Mitigation direction
- Review the Microsoft MSRC advisory for applicable security updates and deployment guidance.
- Prioritize remediation for internet-facing or high-use SharePoint 2016 and 2019 farms.
- Restrict SharePoint access to trusted users and networks where business requirements allow.
- Monitor Microsoft guidance for any updated mitigation or patch information.
Validation and detection
- Inventory SharePoint Enterprise Server 2016 and SharePoint Server 2019 deployments.
- Compare installed SharePoint update levels against the Microsoft MSRC advisory.
- Identify internet-facing SharePoint sites and high-privilege collaboration areas.
- Review security logs for unusual crafted requests or reported XSS behavior.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2020-1099 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 5.4 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N2.32.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.4MediumVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-1099CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.