How severe is CVE-2015-8766?

CVE-2015-8766 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2015-8766?

CVE-2015-8766 affects the following packages: symphonycms/symphony-2 (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2015-8766?

Update symphonycms/symphony-2 to 2.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2015-8766 is resolved across your whole dependency graph.

How do I detect CVE-2015-8766 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symphonycms/symphony-2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2015-8766 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2015-8766 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2015-8766, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2015-8766?

CVE-2015-8766 has an EPSS (Exploit Prediction Scoring System) score of 1.8%, placing it in the 78th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2015-8766?

CVE-2015-8766 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2015-8766 published, and has it been updated?

CVE-2015-8766 was published on May 13, 2022 and was last updated on February 17, 2024. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

MEDIUM severity

CVE-2015-8766 — symphony-2

MEDIUMFix: symphonycms/symphony-2@651e150

CVE-2015-8766 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in symphonycms/symphony-2. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for symphonycms/symphony-2 — see the affected versions and patch details below.

Symphony CMS XSS Vulnerabilities

Published

May 13, 2022

Updated

Feb 17, 2024

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs78th percentile — riskier than 78% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

🐘symphonycms/symphony-2

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Multiple cross-site scripting (XSS) vulnerabilities in content/content.systempreferences.php in Symphony CMS before 2.6.4 allow remote attackers to inject arbitrary web script or HTML via the (1) email_sendmail[from_name], (2) email_sendmail[from_address], (3) email_smtp[from_name], (4) email_smtp[from_address], (5) email_smtp[host], (6) email_smtp[port], (7) jit_image_manipulation[trusted_external_sites], or (8) maintenance_mode[ip_whitelist] parameters to system/preferences.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`symphonycms/symphony-2`	all versions	2.6.4`composer require symphonycms/symphony-2:^2.6.4`

Affected Products

1 product · 1 configurations

Application

symphonygetsymphony

≤ 2.6.3

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Multiple cross-site scripting (XSS) vulnerabilities in content/content.s…

seclists.orgNVDOct 2020

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for symphonycms/symphony-2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update symphonycms/symphony-2 to 2.6.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2015-8766 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

Multiple cross-site scripting (XSS) vulnerabilities in `content/content.systempreferences.php` in Symphony CMS before 2.6.4 allow remote attackers to inject arbitrary web script or HTML via the (1) `email_sendmail[from_name]`, (2) `email_sendmail[from_address]`, (3) `email_smtp[from_name]`, (4) `email_smtp[from_address]`, (5) `email_smtp[host]`, (6) `email_smtp[port]`, (7) `jit_image_manipulation[trusted_external_sites]`, or (8) `maintenance_mode[ip_whitelist]` parameters to system/preferences.

O3 Security · Impact-Aware SCA

Is CVE-2015-8766 in your dependencies?

Find it across Packagist, including transitive dependencies.

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CVSS Score

6.1/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Raw vector

CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CWE Classification

CWE-79Cross-site Scripting (XSS)

Weaponization

No Nuclei template or Metasploit module yet. 1 public proof-of-concept reference is listed on this page.

Timeline

First exploit

Oct 29, 2020

Disclosed

May 13, 2022

Last updated

Feb 17, 2024

Identifiers

CVE-2015-8766

References

Advisorynvd.nist.gov · CVE 2015 8766 Webgithub.com · 651e150091c61fb60ad1dff2bc2166185a83d9d6 Webweb.archive.org · cve 2015 8766 getsymphoney Webseclists.org Webgetsymphony.com · 2.6.4 Packagegithub.com · symphony 2

Related vulnerabilities

Also affects symphonycms/symphony-2

This CVE is medium severity — higher than any of the other 1 CVE affecting symphonycms/symphony-2 (highest there: low).

CVE-2011-4340

Same weakness: CWE-79

This CVE is medium severity; 7 of 7 other CVEs with CWE-79 are rated as high or higher (top: critical).

CVE-2026-55649CVE-2026-113787CVE-2026-44267CVE-2026-96632CVE-2026-9086CVE-2026-118246CVE-2026-118251Browse all CWE-79

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedFeb 17, 2024