CVE-2026-76098

Mistune is a Python Markdown parser with renderers and plugins. Versions 3.3.0 through 3.3.2 are vulnerable to DoS through deeply nested tokens. HTML rendering creates deeply nested emphasis tokens from consecutive asterisk characters, and recursive rendering in HTMLRenderer.rendertoken can excee...

GHSA-QFRW-5RXM-MHH2 Mistune renderers/html.safe_url: HARMFUL_PROTOCOLS list misses legacy and chained schemes that historically chain to `javascript:` execution

Summary Type: URL-scheme allowlist gap. The safeurl filter only blocks the four schemes javascript:, vbscript:, file:, data:. Several other schemes are accepted into rendered and tags despite being known XSS vectors in legacy or chain-handling browsers. The same gap applies to direct links,...

GHSA-G97X-GVCM-X72H Mistune: XSS via unescaped class option in Admonition directive

In src/mistune/directives/admonition.py, the renderadmonition function concatenates the :class: option directly into the HTML class attribute without escaping lines 63-68. This allows attribute injection and XSS even when HTMLRendererescape=True is used. The directive name parameter is safe...

GHSA-8C25-4J27-2RV3 Mistune: XSS via percent-encoded javascript URI bypass in safe_url()

Summary An XSS vulnerability in Mistune allows bypassing of safeurl protections via percent-encoded javascript URIs. Details The vulnerability exists in HTMLRenderer.safeurl in Mistune. The function is intended to block harmful URL schemes such as "javascript:" by checking the prefix of the...

CVE-2026-59923

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.3.0, HTMLRenderer.safeurl does not block percent-encoded javascript URIs, allowing attacker-supplied Markdown links or images to bypass URL protections and execute script in rendered HTML. This issue is fixed in version...

CVE-2026-44897

Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, HTMLRenderer.heading builds the opening tag by string-concatenating the id attribute value directly into the HTML — with no call to escape, safeentity, or any other sanitisation function. A double-quote character " in...

Cross-site Scripting (XSS)

Overview Affected versions of this package are vulnerable to Cross-site Scripting XSS via the HTMLRenderer heading rendering path in the HTML renderer. An attacker can inject arbitrary HTML by supplying a heading id attribute value that contains quotes and markup. The rendered output can be alter...

GHSA-V87V-83H2-53W7 Mistune Heading ID Attribute has Injection XSS

Summary HTMLRenderer.heading builds the opening tag by string-concatenating the id attribute value directly into the HTML — with no call to escape, safeentity, or any other sanitisation function. A double-quote character " in the id value terminates the attribute, allowing an attacker to inject...

MAL-2024-1579 Malicious code in mmsdk-apml-htmlrenderer (npm)

--- -= Per source details. Do not edit below this line.=- Source: ghsa-malware ae0814f13d1d5f49711b30a6fe260c2bfb566047df1b02774e899421faf58c92 Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be...

Malicious code in mmsdk-apml-htmlrenderer (npm)

--- -= Per source details. Do not edit below this line.=- Source: ghsa-malware ae0814f13d1d5f49711b30a6fe260c2bfb566047df1b02774e899421faf58c92 Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be...