Run static analysis (SAST) on the codebase looking for the unsafe pattern in the data flow.
CWE-82 Variant Incomplete
Improper Neutralization of Script in Attributes of IMG Tags in a Web Page
This vulnerability occurs when a web application fails to properly sanitize or escape script code within the attributes of HTML IMG tags, such as the 'src' attribute.
Definition
What is CWE-82?
This vulnerability occurs when a web application fails to properly sanitize or escape script code within the attributes of HTML IMG tags, such as the 'src' attribute.
Attackers can inject malicious scripts (XSS) into seemingly harmless image tag attributes. When a victim's browser loads the compromised page, it processes the tainted attribute and executes the injected code, often without any visible indication to the user.
This type of attack exploits the trust a browser has in content served by the application. To prevent it, developers must rigorously validate and encode all user-supplied data before it is inserted into HTML attributes, treating attribute values as untrusted by default.
Real-world impact
Real-world CVEs caused by CWE-82
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Stored XSS in a guestbook application using a javascript: URI in a bbcode img tag.
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javascript URI scheme in IMG tag.
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javascript URI scheme in IMG tag.
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javascript URI scheme in IMG tag.
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javascript URI scheme in IMG tag.
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javascript URI scheme in IMG tag.
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javascript URI scheme in IMG tag.
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javascript URI scheme in IMG tag.
How attackers exploit it
Step-by-step attacker path
- 1
Identify a code path that handles untrusted input without validation.
- 2
Craft a payload that exercises the unsafe behavior — injection, traversal, overflow, or logic abuse.
- 3
Deliver the payload through a normal request and observe the application's reaction.
- 4
Iterate until the response leaks data, executes attacker code, or escalates privileges.
Vulnerable code example
Vulnerable pseudo
MITRE has not published a code example for this CWE. The pattern below is illustrative — see Resources for canonical references.
// Example pattern — see MITRE for the canonical references.
function handleRequest(input) {
// Untrusted input flows directly into the sensitive sink.
return executeUnsafe(input);
} Secure code example
Secure pseudo
// Validate, sanitize, or use a safe API before reaching the sink.
function handleRequest(input) {
const safe = validateAndEscape(input);
return executeWithGuards(safe);
} What changed: the unsafe sink is replaced (or the input is validated/escaped) so the same payload no longer triggers the weakness.
Prevention checklist
How to prevent CWE-82
- Implementation Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component. The problem of inconsistent output encodings often arises in web pages. If an encoding is not specified in an HTTP header, web browsers often guess about which encoding is being used. This can open up the browser to subtle XSS attacks.
- Implementation To help mitigate XSS attacks against the user's session cookie, set the session cookie to be HttpOnly. In browsers that support the HttpOnly feature (such as more recent versions of Internet Explorer and Firefox), this attribute can prevent the user's session cookie from being accessible to malicious client-side scripts that use document.cookie. This is not a complete solution, since HttpOnly is not supported by all browsers. More importantly, XMLHTTPRequest and other powerful browser technologies provide read access to HTTP headers, including the Set-Cookie header in which the HttpOnly flag is set.
Detection signals
How to detect CWE-82
Run dynamic application security testing against the live endpoint.
Watch runtime logs for unusual exception traces, malformed input, or authorization bypass attempts.
Code review: flag any new code that handles input from this surface without using the validated framework helpers.
Plexicus auto-detects CWE-82 and opens a fix PR in under 60 seconds.
Codex Remedium scans every commit, identifies this exact weakness, and ships a reviewer-ready pull request with the patch. No tickets. No hand-offs.
Frequently asked questions What is CWE-82?
How serious is CWE-82?
What languages or platforms are affected by CWE-82?
How can I prevent CWE-82?
How does Plexicus detect and fix CWE-82?
Where can I learn more about CWE-82?
Frequently asked questions
What is CWE-82?
This vulnerability occurs when a web application fails to properly sanitize or escape script code within the attributes of HTML IMG tags, such as the 'src' attribute.
How serious is CWE-82?
MITRE has not published a likelihood-of-exploit rating for this weakness. Treat it as medium-impact until your threat model proves otherwise.
What languages or platforms are affected by CWE-82?
MITRE has not specified affected platforms for this CWE — it can apply across most application stacks.
How can I prevent CWE-82?
Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special,…
How does Plexicus detect and fix CWE-82?
Plexicus's SAST engine matches the data-flow signature for CWE-82 on every commit. When a match is found, our Codex Remedium agent opens a fix PR with the corrected code, tests, and a one-line summary for the reviewer.
Where can I learn more about CWE-82?
MITRE publishes the canonical definition at https://cwe.mitre.org/data/definitions/82.html. You can also reference OWASP and NIST documentation for adjacent guidance.
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