Ckeditor4: When bbcode tags aren't terminated it breaks completly the editor

[xillibit]

Type of report

Bug

Provide detailed reproduction steps (if any)

1. you have by example this code in source : [b]Hello world![/b]
2. then modifiy it to : [b]Hello world![/b
3. go in normal mode, change to [b]Hello world![/b]
4. go into source, CKeditor fails and you have nothing in edit area

Expected result

The editor shouldn't fails completly

Actual result

The editor fails completly and you that in browser console :

Uncaught TypeError: candidate is null in plugins/bbcode/plugin.js:344:16
onTagClose file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/bbcode/plugin.js:344
parse file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/bbcode/plugin.js:171
fromBBCode file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/bbcode/plugin.js:408
BBCodeToHtml file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/bbcode/plugin.js:588
onSetData file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/bbcode/plugin.js:763
listenerFirer file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/event.js:169
fire file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/event.js:313
fire file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/editor_basic.js:24
setData file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/editor.js:1152
onLoad file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/wysiwygarea/plugin.js:97
listenerFirer file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/event.js:169
fire file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/event.js:313
getNativeListener file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/dom/domobject.js:46
on file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/dom/domobject.js:93
init file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/wysiwygarea/plugin.js:52
setMode file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/creators/themedui.js:225
exec file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/sourcearea/plugin.js:145
exec file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/command.js:56
execCommand file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/editor.js:983
click file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/button/plugin.js:87
execute file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/button/plugin.js:165
clickFn file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/plugins/button/plugin.js:197
addFunction file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/tools.js:828
callFunction file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/core/tools.js:856
onclick file:///C:/Users/xillibit/Downloads/ckeditor_4.16.1_41a8791ce01b_source_big/ckeditor/samples/index.html:1

Other details

• Browser: Firefox 88.0.1
• OS: Windows 10 21H1
• CKEditor version: 4.16.1
• Installed CKEditor plugins: bbcode

[sculpt0r]

Hi @xillibit ,

Thank you for the report. I try to follow the steps you provide and I'm kind of lost. Could you confirm my version:
1.Put [b]Hello·world![/b as editor content in HTML.

1. Open the editor. The text is bolded, including improper closing bbcode tag [/b
2. Add missing ] to the incorrectly closed tag [/b.
3. Switch to sourcemode.
4. Switch to normal mode.

Now editor hangs with errors in the console.

[xillibit]

Yes it's like that, i hadn't added the error showed in the console when the editor hangs. I have added it in my issue above

[f1ames]

The source data is interesting in the gif from https://github.com/ckeditor/ckeditor4/issues/4730#issuecomment-849459732:

<b>Hello·world![/b</b>

Since the editor uses bbcode plugin, I think output should contain bbcode only (so [b]) instead of <b> which may mean there is more complex issue somewhere deeper related to how invalid bbcode is parsed :thinking:

[sculpt0r]

@xillibit - thank you for confirmation. Now I can properly label this issue.

@f1ames - definitely looks more complex... I mark it with proper size label :+1:

[blackcoder87]

Probably related to this if not the same:
https://github.com/ckeditor/ckeditor4/issues/2782