Security readout for executives and security teams
Plain-English summary
Apostrophe CMS had a stored cross-site scripting issue where an editor could upload a malicious SVG through the Images module. The script could run when another user viewed it. Business risk is mainly session abuse, content tampering, or limited data exposure inside the CMS.
Executive priority
Treat as a medium-priority CMS security issue. Remediate promptly, especially on sites with many editors, agencies, contractors, or shared content workflows.
Technical view
CVE-2021-25978 is CWE-79 stored XSS in Apostrophe CMS versions reported between 2.63.0 and 3.3.1. Attack requires low privileges and user interaction. The CVSS 3.1 score is 5.4 with changed scope, low confidentiality and integrity impact, and no availability impact.
Likely exposure
Exposure is likely limited to Apostrophe CMS deployments in the affected version range where editors can upload SVG files to the Images module. Risk increases when many semi-trusted users have editor access.
Exploitation context
The supplied sources do not show CISA KEV listing or active exploitation. Exploitation requires an authenticated editor to upload a crafted SVG and another user to view it.
Researcher notes
Evidence identifies stored XSS through SVG upload and a related GitHub commit. The bundle does not include a detailed advisory, exploit proof, or explicit patch version statement, so avoid assumptions beyond the affected range and referenced fix.
Mitigation direction
- Check Apostrophe vendor guidance and update beyond affected versions where supported.
- Review the referenced upstream commit for the vendor’s intended fix.
- Restrict SVG uploads to trusted administrators until patched.
- Audit editor accounts and remove unnecessary image upload permissions.
- Review existing uploaded SVG files for suspicious content.
Validation and detection
- Inventory Apostrophe CMS versions across public and internal sites.
- Confirm whether the Images module accepts SVG uploads from editor roles.
- Check whether deployments are within 2.63.0 through 3.3.1.
- Review CMS logs for unusual SVG uploads by editor accounts.
- Test remediation in staging with safe XSS regression cases only.
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-2021-25978 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://github.com/apostrophecms/apostrophe/commit/c8b94ee9c79468f1ce28e31966cb0e0839165e59CVE 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.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.