Beautiful Soup

BeautifulSoup._popToTag will pop every tag in the document if given a mismatched end tag

Bug #1880420 reported by Leonard Richardson
6
This bug affects 1 person
Affects Status Importance Assigned to Milestone
Beautiful Soup
Fix Released
Undecided
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Bug Description

Code to reproduce:

---
from bs4 import BeautifulSoup
data = """<html><div>b</div></span>c"""
print(BeautifulSoup(data, 'html.parser'))
---

Output:

---
<html><div>b</div></html>c
---

The markup '</span>' makes html.parser call BeautifulSoupHTMLParser.handle_endtag, which calls BeautifulSoup.handle_endtag, which calls BeautifulSoup._popToTag('span'). Since there is no open <span> tag in the stack, every tag in the stack gets popped, including <html>. Parsing of the document then proceeds even though </html> is supposed to signify the end of the document.

This is only a problem when using html.parser, since lxml and html5lib know not to treat "</span>" as a real closing tag.

One solution that wouldn't hurt performance much would be to keep a Counter of tag names, and to make _popToTag a no-op if the tag name isn't in the Counter. (It needs to be a Counter so we can keep track of nested tags with the same name while still keeping constant-time lookups.)

Revision history for this message
Leonard Richardson (leonardr) wrote :

Revision 579 has a fix.

Changed in beautifulsoup:
status: New → Fix Committed
Leonard Richardson (leonardr)
Changed in beautifulsoup:
status: Fix Committed → Fix Released
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