VulnerabilityPublished 23 Jun 2025

CVE-2025-52561: JuliaComputing HTMLSanitizer.jl · Cross-site Scripting

Affects JuliaComputing HTMLSanitizer.jlSource CVE Database V5

Not known to be exploited · CVSS 6.9 Medium : upgrade to 0.2.1 when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 4.0 base score

6.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.8% chance of exploitation in 30 days – higher than 58% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.2.1

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: Low
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 23 Jun 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade github.com/juliacomputing/HTMLSanitizer.jl to 0.2.1.

Affected software

Product	Affected	Fixed in
Gogithub.com/juliacomputing/HTMLSanitizer.jl`pkg:golang/github.com/juliacomputing/HTMLSanitizer.jl`Other threats	Affected <0.2.1	Fixed in 0.2.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Immediate upgrade to HTMLSanitizer.jl version 0.2.1 or later to apply the official patch that corrects the unescaping behavior inside the <style> tag.
As an interim measure, manually add the <math> and <svg> elements to the whitelist in the sanitizer configuration to reduce the attack surface.
Conduct a thorough audit of all web applications and services using HTMLSanitizer.jl to identify vulnerable versions and usage contexts.
Implement Content Security Policy (CSP) headers with strict script-src directives to restrict the execution of unauthorized scripts, mitigating the impact of potential XSS attacks.
Employ runtime application self-protection (RASP) or web application firewalls (WAFs) configured to detect and block suspicious HTML or script injection attempts targeting the sanitizer.
Educate developers on secure coding practices related to input sanitization and output encoding, emphasizing the risks of improper whitelist configurations.
Monitor security advisories and threat intelligence feeds for any emerging exploit attempts targeting this vulnerability to enable rapid response.

Description

HTMLSanitizer.jl is a Whitelist-based HTML sanitizer. Prior to version 0.2.1, when adding the style tag to the whitelist, content inside the tag is incorrectly unescaped, and closing tags injected as content are interpreted as real HTML, enabling tag injection and JavaScript execution. This could result in possible cross-site scripting (XSS) in any HTML that is sanitized with this library. This issue has been patched in version 0.2.1. A workaround involves adding the math and svg elements to the whitelist manually.

Impact

For European organizations, this vulnerability poses a significant risk primarily to web applications and services that incorporate the HTMLSanitizer.jl library for sanitizing user-generated or external HTML content. Exploitation could lead to unauthorized script execution in users' browsers, enabling attackers to steal sensitive information such as session cookies, perform actions on behalf of users (CSRF), or deliver malware. This can compromise confidentiality and integrity of user data and potentially disrupt service availability if leveraged for further attacks. Organizations in sectors with high web interaction, such as finance, e-commerce, healthcare, and government services, are particularly at risk. The medium severity score indicates a moderate but non-trivial threat level, especially given the lack of required authentication or user interaction. The absence of known exploits suggests limited immediate risk, but the vulnerability's nature means it could be weaponized quickly once discovered by attackers. Failure to patch or mitigate could lead to reputational damage, regulatory penalties under GDPR if personal data is compromised, and operational disruptions.

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 23 Jun 2025, 21:18 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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