Security readout for executives and security teams
Plain-English summary
This is a cross-site scripting issue in Joomla CMS error pages. Affected Joomla 3.0.0 through 3.9.25 did not adequately escape the logo parameter in default templates, allowing attacker-controlled script content to be rendered in a user’s browser.
Executive priority
Prioritize remediation for internet-facing Joomla sites, but this is not supported as emergency-level from the provided evidence. The main business risk is user-session or trust compromise through browser-executed script on vulnerable error pages.
Technical view
CVE-2021-26030 affects Joomla CMS 3.0.0-3.9.25. The flaw is inadequate output escaping for the logo parameter on default-template error pages, creating an XSS condition. The provided sources do not include CVSS, CWE, fixed-version, or detailed exploitation prerequisites.
Likely exposure
Public Joomla sites running versions 3.0.0 through 3.9.25 are the relevant exposure group, especially where default templates and error pages are reachable. Sites on later or vendor-confirmed fixed releases are not indicated as affected in the supplied bundle.
Exploitation context
The bundle does not show CISA KEV listing or any cited evidence of active exploitation. Treat this as a plausible web XSS exposure, but do not claim known exploitation from the provided evidence.
Researcher notes
Evidence is thin: no CVSS, CWE, fixed version, or exploitation telemetry is included in the bundle. The strongest grounded facts are the affected Joomla range, default-template error-page context, and logo-parameter escaping failure.
Mitigation direction
- Inventory Joomla CMS versions across public sites.
- Check Joomla vendor guidance for the fixed release path.
- Upgrade affected Joomla 3.0.0-3.9.25 installations to a vendor-supported fixed version.
- Review custom error templates for equivalent unsafe parameter rendering.
- Monitor web logs for suspicious error-page parameter activity.
Validation and detection
- Confirm whether each Joomla instance runs 3.0.0 through 3.9.25.
- Verify whether default templates are used for error pages.
- Confirm remediation against Joomla’s official advisory or release notes.
- Run authenticated, non-destructive XSS scanning after patching.
- Document any exposed legacy Joomla instances for priority remediation.
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.
CVE-2021-26030 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
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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 and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://developer.joomla.org/security-centre/850-20210401-core-escape-xss-in-logo-parameter-error-pages.htmlCVE reference · x_refsource_MISC, vendor-advisory
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.