Skip to content

fix: escape HTML attributes to prevent XSS attacks #1741

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
laurentgoudet wants to merge 1 commit into
base: master
Choose a base branch
from
Open

fix: escape HTML attributes to prevent XSS attacks #1741

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
28 changes: 24 additions & 4 deletions src/lg-utils.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -388,6 +388,20 @@ const utils = {
return transform;
},

/**
* Escapes HTML attribute values to prevent XSS attacks
* @param {string} value - The attribute value to escape
* @returns {string} The escaped attribute value
*/
escapeHtml(value: string): string {
return value
.replace(/&/g, '&')
.replace(/</g, '&lt;')
.replace(/>/g, '&gt;')
.replace(/"/g, '&quot;')
.replace(/'/g, '&#x27;');
},

getIframeMarkup(
iframeWidth: string,
iframeHeight: string,
Expand All @@ -396,7 +410,9 @@ const utils = {
src?: string,
iframeTitle?: string,
): string {
const title = iframeTitle ? 'title="' + iframeTitle + '"' : '';
const title = iframeTitle
? 'title="' + this.escapeHtml(iframeTitle) + '"'
: '';
return `<div class="lg-media-cont lg-has-iframe" style="width:${iframeWidth}; max-width:${iframeMaxWidth}; height: ${iframeHeight}; max-height:${iframeMaxHeight}">
<iframe class="lg-object" frameborder="0" ${title} src="${src}" allowfullscreen="true"></iframe>
</div>`;
Expand All @@ -410,8 +426,8 @@ const utils = {
sizes?: string,
sources?: ImageSources[],
): string {
const srcsetAttr = srcset ? `srcset="${srcset}"` : '';
const sizesAttr = sizes ? `sizes="${sizes}"` : '';
const srcsetAttr = srcset ? `srcset="${this.escapeHtml(srcset)}"` : '';
const sizesAttr = sizes ? `sizes="${this.escapeHtml(sizes)}"` : '';
const imgMarkup = `<img ${altAttr} ${srcsetAttr} ${sizesAttr} class="lg-object lg-image" data-index="${index}" src="${src}" />`;
let sourceTag = '';
if (sources) {
Expand Down Expand Up @@ -574,7 +590,11 @@ const utils = {
dynamicEl.thumb = thumb;

if (getCaptionFromTitleOrAlt && !dynamicEl.subHtml) {
dynamicEl.subHtml = title || alt || '';
// Escape HTML when using title/alt as caption to prevent XSS
const captionText = title || alt || '';
dynamicEl.subHtml = captionText
? this.escapeHtml(captionText)
: '';
}
dynamicEl.alt = alt || title || '';
dynamicElements.push(dynamicEl);
Expand Down
4 changes: 2 additions & 2 deletions src/lightgallery.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1004,13 +1004,13 @@ export class LightGallery {
// Use the thumbnail as dummy image which will be resized to actual image size and
// displayed on top of actual image
let imgContent: string | HTMLImageElement = '';
const altAttr = alt ? 'alt="' + alt + '"' : '';
const altAttr = alt ? 'alt="' + utils.escapeHtml(alt) + '"' : '';

if (this.isFirstSlideWithZoomAnimation()) {
imgContent = this.getDummyImageContent(
$currentSlide,
index,
altAttr,
alt || '',
);
} else {
imgContent = utils.getImgMarkup(
Expand Down
219 changes: 219 additions & 0 deletions test/lightgallery.test.ts
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -302,3 +302,222 @@ describe('Plugins', () => {
expect(LG.galleryItems[0].poster).toBeUndefined();
});
});

describe('Security - XSS Prevention', () => {
it('Should escape double quotes in alt attribute to prevent attribute breakout', async () => {
// Test: Double quote to break out of attribute and inject malicious HTML
document.body.innerHTML = `<div id="lightGallery">
<a href="a.png">
<img src="b.png" alt='"><img src=x onerror=alert(1)>' />
</a>
</div>`;

const LG = lightGallery(
document.getElementById('lightGallery') as HTMLElement,
);
LG.openGallery(0);

await waitFor(() => {
const lgObject = document.querySelector('.lg-object');
expect(lgObject).toBeInTheDocument();

if (lgObject) {
const altValue = lgObject.getAttribute('alt');
expect(altValue).toBe('"><img src=x onerror=alert(1)>');
}

// Verify no malicious img was injected
const xssImg = document.querySelector('img[src="x"]');
expect(xssImg).toBeNull();
});

LG.destroy();
});

it('Should escape double quotes in alt to prevent event handler injection', async () => {
// Test: Inject onload event handler
document.body.innerHTML = `<div id="lightGallery">
<a href="a.png">
<img src="b.png" alt='" onload="alert(1)" x="' />
</a>
</div>`;

const LG = lightGallery(
document.getElementById('lightGallery') as HTMLElement,
);
LG.openGallery(0);

await waitFor(() => {
const lgObject = document.querySelector('.lg-object');
expect(lgObject).toBeInTheDocument();

if (lgObject) {
const altValue = lgObject.getAttribute('alt');
expect(altValue).toBe('" onload="alert(1)" x="');

// The onload should not be an actual attribute
expect(lgObject.hasAttribute('onload')).toBe(false);
}
});

LG.destroy();
});

it('Should escape double quotes in alt to prevent script injection', async () => {
// Test: Script tag injection
document.body.innerHTML = `<div id="lightGallery">
<a href="a.png">
<img src="b.png" alt='"><script>alert("XSS")</script><img x="' />
</a>
</div>`;

const LG = lightGallery(
document.getElementById('lightGallery') as HTMLElement,
);
LG.openGallery(0);

await waitFor(() => {
const lgObject = document.querySelector('.lg-object');
expect(lgObject).toBeInTheDocument();

// No script tags should be injected
const scripts = document.querySelectorAll('.lg-item script');
expect(scripts.length).toBe(0);
});

LG.destroy();
});

it('Should handle ampersands in alt without double-encoding', async () => {
// Test: Special HTML characters
document.body.innerHTML = `<div id="lightGallery">
<a href="a.png">
<img src="b.png" alt="Testing &amp; signs &lt; and &gt; symbols" />
</a>
</div>`;

const LG = lightGallery(
document.getElementById('lightGallery') as HTMLElement,
);
LG.openGallery(0);

await waitFor(() => {
const lgObject = document.querySelector('.lg-object');
expect(lgObject).toBeInTheDocument();

if (lgObject) {
const altValue = lgObject.getAttribute('alt');
// Browser automatically decodes HTML entities in attributes
expect(altValue).toBe('Testing & signs < and > symbols');
}
});

LG.destroy();
});

it('Should handle single quotes in alt attribute', async () => {
// Test: Single quotes (less dangerous but should still work)
document.body.innerHTML = `<div id="lightGallery">
<a href="a.png">
<img src="b.png" alt="It's a nice image with 'quotes'" />
</a>
</div>`;

const LG = lightGallery(
document.getElementById('lightGallery') as HTMLElement,
);
LG.openGallery(0);

await waitFor(() => {
const lgObject = document.querySelector('.lg-object');
expect(lgObject).toBeInTheDocument();

if (lgObject) {
const altValue = lgObject.getAttribute('alt');
expect(altValue).toBe("It's a nice image with 'quotes'");
}
});

LG.destroy();
});

it('Should escape double quotes in srcset attribute', async () => {
// Test: Srcset attribute vulnerability
document.body.innerHTML = `<div id="lightGallery">
<a href="a.png">
<img src="b.png" srcset='" onload="alert(1)" x="' />
</a>
</div>`;

const LG = lightGallery(
document.getElementById('lightGallery') as HTMLElement,
);
LG.openGallery(0);

await waitFor(() => {
const lgObject = document.querySelector('.lg-object');
expect(lgObject).toBeInTheDocument();

if (lgObject) {
// Should not have onload as an actual attribute
expect(lgObject.hasAttribute('onload')).toBe(false);
}
});

LG.destroy();
});

it('Should escape double quotes in sizes attribute', async () => {
// Test: Sizes attribute vulnerability
document.body.innerHTML = `<div id="lightGallery">
<a href="a.png">
<img src="b.png" sizes='" onload="alert(1)" x="' />
</a>
</div>`;

const LG = lightGallery(
document.getElementById('lightGallery') as HTMLElement,
);
LG.openGallery(0);

await waitFor(() => {
const lgObject = document.querySelector('.lg-object');
expect(lgObject).toBeInTheDocument();

if (lgObject) {
// Should not have onload as an actual attribute
expect(lgObject.hasAttribute('onload')).toBe(false);
}
});

LG.destroy();
});

it('Should handle backslashes and special characters in alt', async () => {
// Test: Various escape characters
document.body.innerHTML = `<div id="lightGallery">
<a href="a.png">
<img src="b.png" alt='Test \\ backslash and "quotes" and <tags>' />
</a>
</div>`;

const LG = lightGallery(
document.getElementById('lightGallery') as HTMLElement,
);
LG.openGallery(0);

await waitFor(() => {
const lgObject = document.querySelector('.lg-object');
expect(lgObject).toBeInTheDocument();

if (lgObject) {
const altValue = lgObject.getAttribute('alt');
// Should preserve the content as-is
expect(altValue).toContain('backslash');
expect(altValue).toContain('quotes');
}
});

LG.destroy();
});
});